PC archeology: The Leading Edge MP-2400L doesn't exist

It's not surprising when you can't find any information about a computer from a small unknown company. This is different. The computer computer in this video was sold by Leading Edge, a rather prolific and popular PC clone maker. It honestly baffles my mind that there appears to be zero information about the existence of this machine on the internet. That changes now!
-- Info
Leading Edge MP-2400L
Mitsubishi PC13WA Power supply
Mitsubishi F504A-372 1.2mb Floppy Drive
Toshiba FDD6882E 1.2mb floppy drive
Fujitsu Limited M2553K 1.2mb floppy drive
DIP switch settings:
1 and 2: CPU SPEED / WAIT STATE:
ON / ON = 8mhz 1WS
OFF / OFF = 6mhz 1WA
ON / OFF = 6mhz 0WS
OFF / ON = 7.17mhz 0WS (fastest mode)
3: ON = 512k conv. / 512k extended OFF = 640k conv / 0k extended
4: ? Should probably be "Off"
5 and 6: RAM SIZE OFF / OFF = 1 meg
7: Keyboard, must always be ON
8: Monitor type?
-- Links
My patrons found this Mitsubishi motherboard which seems to have similar DIP switches:
stason.org/TUL...
Video showing 286 battery upgrade:
• This easy IBM 5170 upg...
Hard drive testing video
• I ran into so many iss...
GSETUP:
www.minuszerod...
CMOS reset procedure:
www.minuszerod...
BIOS dump:
archive.org/de...
Adrian's Digital Basement Merch store:
my-store-c82bd...
Adrian's Digital Basement ][ (Second Channel)
/ @adriansdigitalbasement2
Support the channel on Patreon:
/ adriansdigitalbasement
-- Tools
Deoxit D5:
amzn.to/2VvOKy1
store.caig.com/...
O-Ring Pick Set: (I use these to lift chips off boards)
amzn.to/3a9x54J
Elenco Electronics LP-560 Logic Probe:
amzn.to/2VrT5lW
Hakko FR301 Desoldering Iron:
amzn.to/2ye6xC0
Rigol DS1054Z Four Channel Oscilloscope:
www.rigolna.co...
Head Worn Magnifying Goggles / Dual Lens Flip-In Head Magnifier:
amzn.to/3adRbuy
TL866II Plus Chip Tester and EPROM programmer: (The MiniPro)
amzn.to/2wG4tlP
www.aliexpress...
TS100 Soldering Iron:
amzn.to/2K36dJ5
www.ebay.com/i...
EEVBlog 121GW Multimeter:
www.eevblog.co...
DSLogic Basic Logic Analyzer:
amzn.to/2RDSDQw
www.ebay.com/i...
Magnetic Screw Holder:
amzn.to/3b8LOhG
www.harborfrei...
Universal ZIP sockets: (clones, used on my ZIF-64 test machine)
www.ebay.com/i...
RetroTink 2X Upconverter: (to hook up something like a C64 to HDMI)
www.retrotink.com/
Plato (Clone) Side Cutters: (order five)
www.ebay.com/i...
Heat Sinks:
www.aliexpress...
Little squeezy bottles: (available elsewhere too)
amzn.to/3b8LOOI
--- Links
My GitHub repository:
github.com/mis...
Commodore Computer Club / Vancouver, WA - Portland, OR - PDX Commodore Users Group
www.commodorec...
--- Instructional videos
My video on damage-free chip removal:
• How to remove chips wi...
--- Music
Intro music and other tracks by:
Nathan Divino
@itsnathandivino

[@adriansdigitalbasement]

Side note -- the one 1986 machine wouldn't run at 7.17mhz at 0 wait states. It would act up and freeze. All the other configurations worked fine. And the two older machines had no problem running at the fast 0 WS mode. Strange!

[@stamasd8500]

Perhaps different brand of memory chips not taking the 0WS well?

[@raypalmer7733]

Adrian, Have you tried the wayback machine to see if anything there is available for the machine?

[@only257]

@@raypalmer7733agreed 😊

[@ruly999]

Would you like another one? I have the Sperry version of this same Mitsubishi PC, glad to donate the entire setup, including monitor, original keyboard and manuals. I'm located in the Portland area.

[@BenState]

retrobrite it?

[@principals16842]

Digital Basement - A shadowy flight into the dangerous world of a PC that does not exist. Adrian Black, a young loner on a crusade to champion the cause of the Commodore, the Tandy, the Macintosh, in a world of computers who operate above 12 volts.

[@redthorne2836]

Random trivia: The theme song hook from Knight Rider is from a ballet.

[@principals16842]

@@redthorne2836 Yes, the March and Procession of Bacchus from "Silvia" by Léo Delibes. We played it in band when I was a freshman in high school and I kept wondering to myself, "Does anyone else hear this? Is it just me?"

[@pyography]

Queue Adrian snatching Comodores, Macs, Tandys from the jaws of the hydraulic press while making moves the Hoff could only dream of to the beat of the 8bit dance party!

[@principals16842]

@@pyography Roundhouse kick to a RIFA cap!

[@amemon43]

​​​@@redthorne2836and the main synthesizer riff in the Knight Rider theme is similar to Sphinx by Harry Thumann

[@jeffymooch]

I just saw a re-run episode of The Price is Right from 1985. They played "One Right Price" or simply the game where you choose from two different price tags. It was played for a Leading Edge PC and a "Computer Cabinet". The two cost 6500 US dollars. Not particularly tech nerdy, but a fun coincidence to see a Leading Edge PC on TV just after this video.

[@miscbits6399]

I had a sanyo MBC 55 about this time. A 1.2Mb floppy drive was over $300 and memory was north of $300/Mb The Japanese computer industry had a mindset that IBM was "the enemy" (they called it "the monster") and the non-IBM form factors were deliberate By 1992 ram had come down to just under USD $50/MB, then the sumitomo resin factory fire occurred and ram doubled in price in a period of less than 2 weeks (just AFTER I'd purchased $2000 worth for resale to Atari users. The company which sold it to me offered to buy back what I hadn't sold for 3 times what I'd paid for it, as they were out of stock and desperate to get systems out the door

[@instazx2]

4:10 -- Hi Adrian! You point out the 6A rating on the power supply. That number is a nameplate rating for an electrical installer, used to size breakers and circuits. If an office was being built out, the electrician would ask how many machines are expected to be installed and used at once, and then divy up the runs to the main panels accordingly. That 6A number will cover the inrush current, and is not the expected operating load. If you have a power outage, every machine plugged into the circuit will surge-draw at once when the power is restored, and you don't want to pull 300A (causing a lot of downstream damage or outages) because you cleverly power-stripped 50 machines onto a single 15A line. You'll see similar ratings on LED power supplies now for the same reason, they're rated like 5A on the input side (600W) even though they're only 350W units at the absolute most.

[@SockyNoob]

Do they still ask those questions today? Or is that just a byproduct of old building codes?

[@thisnthat3530]

It's not just unrush, it's a side effect of the large capacitor bank after the rectifier causing the power supply to only draw current in large spikes just before the peak of the sine wave and nothing in between. Backup generators need to be sized to handle this.

[@miscbits6399]

@@SockyNoob Yes they do and it influences the choice of breaker profile which is used It was about this time that the very "spiky" load of PC switchmode power supplies started to be noticed as causing problems in building distribution systems (it's a similar issue to power factor in industrial settings) and power companies started billing extra for unsmoothed power draw - which rapidly resulted in switchmode supplies with more "linear" power draws being developed

[@AureliusR]

@@miscbits6399 Yes, this is why we put PFC (Power Factor Correction) circuits in switch-mode power supplies. Of course, it's not universal, a lot of cheaper supplies don't bother, but any supply that is targeted at office/industrial use just won't sell without PFC.

[@miscbits6399]

@AureliusR Unfortuinately that hasn't been much of a priority for home systems.. But more to the point for this particular video, I remember that Power Factor issues only became a matter of attention around 1984-5 when the spiky loads were identified as causing serious neutral currents in 3-phase building supplies that the distribution system hadn't been designed for and the need for PFCs started being discussed in both industry and hobbyist media about that time. It got my attention because I was trying to diagnose/mitigate RFI interference from 48V switchmode units (telco digital micriowave systems - DMR) being deployed in/near landmobile hilltop stations. The effects of a forest of rampant switchmode harmonics coupled with fencing wire/staples (most sites were surrounded by 5 wire sheep fencing) acting as (poor) diodes in an environment prone to clouds can cause splatter all the way from 30-500MHz and effectively raise noise floors by 20-40dB (which translates to a loss of ~5-10x range on the receivers, which in turn means extremely angry customers) if they don't completely wipe things out on particular channels (particularly ~100MHz narrowband AM channels).. All the DMR makers had to seriously up their game in terms to attention to RF emissions from components as a result, which played through to most switchmode designs (This was the end result of about 6 months of increasing problems and a few weeks analysis, followed by weeks of trying to mitigate emissions from existing supplies (which kinda worked but it was cheaper to swapout the PSUs at a cost of ~$80million and make it Fujitsu's problem) PFC PC power supplies only became common in the late 1980s and I only started seeing them in typical Taiwanese-sourced clones in the 1990s IE: That box is highly unlikely to have any PFC in it, which means the current profile is spiky, the things emit a LOT of RFI and the inrush current is _high_. Thankfully they predate the badcaps era, but I've still seen a few exploding electrolytics in those generation units

[@jeremiefaucher-goulet3365]

Really cool effect in the intro, with the magically appearing second and third computer.

[@vwestlife]

Paradise was bought out by Western Digital in 1986, so most Paradise video cards and chipsets were made under WD's ownership. Most 287 co-processors run at 2/3rds of the main 286 CPU's clock speed. The 80287-3 chip is rated at 5 MHz, and an 8 MHz 286 system would run it at 5.333 MHz. The 287XL and some of the later non-Intel 287 chips run at the full CPU clock speed.

[@miker252]

I remember spending hours, with my limited knowledge, repairing, adding cards and upgrades to my first XT (picked from junk pile), working out Hard Drive settings, interrupt and DMA conflicts. It was all painfully enjoyable.

[@640-KB]

Have you tried, in gsetup, using the arrow keys on the numeric keypad and/or hitting the numlock key? It's very possible that bios may not support enhanced/extended keyboards and the arrow keys aren't giving the scan codes gsetup wants.

[@paulwierman8078]

This Leading Edge PC is identical to the Sperry PC/IT. I was working for Sperry when they developed a relationship with Mitsubishi and started selling Mitsubishi PCs with the Sperry branding. I bought a fully loaded PC/IT through their employee purchase program. It was my first PC and I still have it albeit in storage. I had to upgrade the BIOS ROM chip in order to run off the shelf Microsoft DOS or OS/2 as the original BIOS was not IBM compatible.

[@orbitaretroretro3907]

Hi. I published on vogons a couple of weeks ago about another Sperry 286. I had been asking for that updated mitsubishi 1.58 bios... if you have it for any chance would you mind sharing it? Thanks

[@miscbits6399]

The Mitsubishi bios (before 1.55) couldn't handle 1.2Mb onboard floppy drives either - that's probably why the addon card was in use. Indications elsewhere are that it's a phoenix bios with Mitsubishi branding If you still have the manuals (especially if they have the dip/jumper settings documented) I think Adrien (and others) would be eternally grateful as there are none online on the usual repositories

[@paulwierman8078]

I will scan my Sperry PC/IT system manual and also make images of the original 1.2M floppies that came with it as soon as I can. The floppies include the Sperry OEM releases of MS-DOS 3.10 & 3.3.0 as well as the CMOS configuration utility. I will look into imaging the ROM BIOS upgrade I got but it is in the system unit which is in storage and a little bit buried. As such this will take a little bit longer. I purchased my system in 1986 and the dip switches are on the back.

[@orbitaretroretro3907]

@@paulwierman8078 that will be great. And of course that can wait :) thanks

[@apfanco]

@@paulwierman8078 would be happy to see all that stuff archived!!

[@KevinDotDay]

The FCC ID on the back label comes up as for a Mitsubishi 9J5MP-2400A computer, with this note on the FCC application "The shielded power cord must be supplied by Mitsubishi. This application includes an optional memory expansion board, two fixed disc drives, and two floppy disc drives." That's another dead end though as far as I could search.

[@adriansdigitalbasement]

Yeah, I'm hoping someone might be able to turn up info on the Japanese domestic version of the machine, if it even exists. I hadn't looked up the FCC ID so too bad that's a dead end too.

[@CoreyDeWalt]

These archeology videos are super entertaining, and makes me very jealous of the machines you find. I also love the proper use of the word "jive", it made me smile.

[@StealthCampADL]

Reminds me of a Sperry machine, it's the right the front panel and vintage. IIRC, it was a somewhat oddball 286. But it's also been 30 odd years, it's just the front panel seems really familiar. Given the amount of badge engineering that went on at the time, it's not impossible that Mitsubishi made these for several vendors.

[@BrooksMoses]

Yeah, someone in another comment said that this was a Mitsubishi design also used by Sperry.

[@briannickel5131]

7.17 MHz is basically 1.5 times the 4.77 MHz speed of the original IBM PC. It was a common speed for turbo XTs.

[@SaraMorgan-ym6ue]

what is unusual about it is that it still works plain and simple🤣🤣🤣

[@leecremeans5446]

It looks like GSETUP is beeping because it can't find the hard disk parameter table in any of the usual places (INT 41h or INT 46h). I poked through the ROM dump and found what looks like a drive parameter table at 0x2fcf; it looks like at least the first few types are standard AT drive types (306/4/17, 615/4/17, etc). You might be able to get GSETUP to work by doing something like "E 0000:0104 CF AF 00 F0" in DEBUG before running GSETUP.

[@adriansdigitalbasement]

I wonder if a patched version could be made? What does that debug command do?

[@leecremeans5446]

@@adriansdigitalbasement It sets INT 41h to where the drive parameter table should be on that bios (assuming the BIOS image starts at F000:8000).

[@adriansdigitalbasement]

@@leecremeans5446 ah pretty trick! According to another viewer it seems the BIOS only supports type 1-14 as well, so a really limited selection which likely explains the strange way these drives were formatted.

[@leecremeans5446]

@@adriansdigitalbasement Okay, I took another look, and it turns out INT 41h doesn't point to the top of the drive parameter table like I thought; it points to the current parameters for drive 0. So I popped GSETUP.EXE open in Ghidra, and yeah, it looks like it's hard-coded to use the AT's drive parameter table address at F000:E401. It looks like the relevant bytes are at 0x274c and 0x274d in the raw EXE; changing the "01 e4" there to "cf af" should make it look in the right place.

[@InsaneWayne355]

The first Leading Edge PCs were Model M's made by Mitsubishi; the model numbers were all MPxxxxL. Later, they switched to Daewoo for manufacturers, which produced the much more common Model D's.

[@ruly999]

As others have mentioned this is the same Mitsubishi PC that Sperry also resold under their brand. I have a complete Sperry 286 system will all original cards and original documentation (including all switches and jumpers). I also have the original Sperry monochrome monitor and an alternate Phoenix BIOS that works in this system. The Mitsubishi BIOS that came with these systems had compatibility issues (for example it will not run Windows) and the Phoenix BIOS seems to work better. If you'd like copies of the documentation or a copy of the Phoenix BIOS let me know. I also have an old Dolche 286 lunchbox system, a DECTalk card and many other old cards and components you can just have as a donation.

[@JE-wd4lu]

My previous comment seems to have never been uploaded. Yes, this is the same model as the Sperry PC/IT. I also happen to have all the documentation for this computer but, unfortunately no floppy disks. It was donated to me some time back when I was looking around for more information on my Sperry HT (or better known as the Leading Edge Model M). Happy to also scan in the Setup Guide's pages as they all came in a binder which is easy to remove for scanning purposes.

[@orbitaretroretro3907]

Could you share that bios publicly at theRetroWeb or some forum like vogons? Thanks a lot

[@ruly999]

@@orbitaretroretro3907 I'll see what I can do. It hasn't been powered up in years.

[@xirabolt]

I have a soft spot for Leading Edge, our first PC was a Leading Edge WinTower 486 with a SoundBlaster 16 (+CDROM) and Colorado tape backup. It eventually got upgraded with an Evergreen Pentium Overdrive processor and Windows 95

[@nchug]

I'm so addicted to your videos❤. Thx.

[@geoffpool7476]

Adrian - This is a great episode! I also have a soft spot for Leading Edge Computers. My Leading Edge Model D is one of my favorites - currently used to demo Minix 1.5. I thought I had seen every type of Leading Edge system until today. Thanks! Greets from Las Vegas.

[@jamesrdgrs]

I love Leading Edge PC's! My first PC was a Leading Edge 486SLC 33Mhz, so many fond and frustrating memories. If it wasn't for that PC I don't know if I would have a career in IT.

[@spewp]

This is a pretty fantastic run through of a PC, thrilled to see this.

[@mkonji8522]

Adrian, I have used several of these back when, however not in the USA but Japan. They were badged as both Mitsubishi as well as Leading Edge as the company I worked for at the time, the company Minolta with the camera and optics division, had several of these to connect up to some equipment we had for testing industrial computer controlled automation. This equipment would populate (if memory serves me correctly) 6 ISA slots each which is why I think we used them at the time as we would also need a video out for display and a controller/memory upgrade combo card. The 3rd 5.25 bay we had populated with a passthrough card slot for some testing equipment that would route to an internally connected ISA slot. This bay also had its own power switch that had to be toggled before the slot card on the front could be inserted or removed as to not short anything. I worked there from 87-91 and not 1 ever had an issue. The monitors that were connected were some industrial rackmount Sanyo displays and the keyboards were black and from Mitsubishi that were extremely clicky and borderline deafening. Not sure I remember much else though as it was a lifetime ago now.

[@Arachnoid_of_the_underverse]

I suggest taking off one of the unused locks an sending it over to lock picking lawyer for an appraisal, Im sure he would be interested.

[@adriansdigitalbasement]

Heh I have an extra lock now from the chassis. I bet he would pick it in mere seconds.

[@Arachnoid_of_the_underverse]

@@adriansdigitalbasement It looks like a simple dimple lock with a possible eight pin settings.

[@SockyNoob]

Probably still better than the best Masterlock

[@0326Hambone]

Wow! The 5170 is the largest and heaviest machine in my collection, I can't imagine what the Leading Edge is like in person! I would LOVE to have one of these!

[@stamasd8500]

I have a 286 machine (well, part of one) which also has a power supply similar to the one in these Leading Edge PCs. The PSU is also very large and heavy, has a very similar shape with an overhang that sits above the motherboard, and uses an even more non-standard power connector for the motherboard. It's a WysePC 286 and I have documented it on the Retro Web website. Including mapping the PSU connector so that if it comes to it, a standard AT power supply could be used with an adapter. Even more interesting in my system is that the CPU oscillator is not on the motherboard. Instead it sits in a little metal box bolted to the side of the PSU at a distance from the motherboard, and outputs 2 clock signals which are carried over to a motherboard header via 2 coaxial cables. I had that documented as well, and in fact it has made it easy to replace the CPU clock with a variable frequency oscillator for easy overclocking and underclocking. :)

[@mikevarry647]

WOW! i remember those from my younger days. I don't remember if I used one, or serviced one, or seen it on display in a store. But I definitely remember those. I love watching your channel. I wish I knew about your channel before discarding some old computer equipment.

[@jakubpolomsky]

There were many funny parts in the video, yet you cracked me up with the WARNING ! ACHTUNG ! part probably the most. Thank you Adrian, had a good time watching this!

[@DiskWizard001]

Some of MFM utilities had an option to manually alter the drives TYPES, without any "before of further" fingertyping. I have an acccess to vast utilities archive, just need to recall the name. It should be WDFMT v 2.10 (AT Disk Format Utility). Cheers, Adrian !

[@hernancoronel]

Hi Adrian! Thanks for the video!

[@tomaswolsink7620]

What an amazing machine! Those motherboards are huge ! Great upload also :)

[@marcelosantos8484]

Plot twist: These old computers used to be metal chassis covered with plastic finish. Nowadays, specially in appliances, you can easily see plastic chassis covered with stainless steel finish. 🙃

[@SockyNoob]

The switch from steel to aluminum PC cases is a godsend though. Once we replaced a 2003 Dell desktop server with a brand new one of the same size and the difference in weight was substantial. We could fit 3 of those servers on a cart, but that single old server made the cart require two people to push and pull. I wager the old server was almost 150 pounds while the new one was closer to 20 or 30. It's not like the new server felt flimsy or anything, still could sit on it.

[@AndrewTubbiolo]

December 1985. I was a sophomore in high school. I think that was the month I purchased my 9" color TV at Crazy Eddie for $79 to support my Commodore 64.

[@eddiehimself]

Most PC cases do use the #6 imperial screws, but the Lian Li PC60 aluminium case I have (same model as LGR's Megaluminum Monster PC), it uses M3 metric screws all round. M3 screws are also used for 3.5" floppy disk drives, optical drives and 2.5" HDDs/SSDs.

[@jasmijndekkers]

Great job Adrian. Greetings from Steven from the Netherlands

[@leecremeans5446]

Another anecdote about these Mitsubishi 286s: When I was in high school, we got a bunch of the smaller versions of these with built-in EGA (I believe Sperry sold them as the PC/microIT). I seem to remember them having similar issues with IBM compatibility, though I haven't played with one in nearly 30 years, so my memory is fuzzy. I *think* we got a hard drive working in one, but I don't remember how.

[@itstheweirdguy]

Wow! The PC speaker is loud and fully functional, premium even! What an experience. That rocks.

[@ypoora1]

I love this machine, so substantial! Since you have two fronts, maybe you should try to retrobrite one? Would really complete this machine's immaculate look.

[@gordon8657]

Mitsubishi built some pretty sturdy components and products in the 80s and 90s. Definitely one of the best manufacturers in Japan for the day.

[@Popashistory]

This looks a lot like a Seanix machine (assembled in Vancouver, British Columbia, Canada). I have to agree with you, setting up the 286 and 386 machines was a real pain, especially if you had to replace the hard-drive. Thanks Adrian

[@davewood4604]

I have seen this before. It was badged as a Sperry then Unisys 286. A long time ago I had the service manual for it.

[@jediknight2350]

great video i loved my 286 many hours playing golf cant remember which one but was awesome.

[@adambourne5523]

My first PC was something VERY similar, unfortunately it went to the great rubbish dump years ago, but you've inspired me to research what model it was!

[@thedungeondelver]

I have to tell you my bus mouse adapter card story. For some damn reason we had a HUGE box of these at a job I worked in the 1990s. Think a box that could easily pack a 14" monitor in it, halfway full of these. Well, this was during the era of the Pentium and Pentium 2, USB becoming common and so forth, so while PS2 mice were the norm all machines had these ports. One Christmas, I grabbed the box and took it in my cube - the walls were that soft felt stuff that was used for sound-deadening, you know what I mean. Anyway, I arranged all the cards into a Christmas tree shape on my cube wall by simply hanging them by the solder points on the back, which snagged the felt quite nicely. I topped it with a squishy stress-ball toy that was in the shape of a star.

[@ohioridercinci2495]

Nice, like I was back in time again. Wondering if you ever ran across a special board. 1. to stop copying disk's mfg's would play with sectors error's and such, non-formatted etc. to overcome this, there was a card called a "copy 2 pc" it would connect between 2 floppy drives and directly copy, keeping sector formatting intact. We used this quite a bit as program sharing was quite common. They tried and we defeated!

[@ovalteen4404]

Friends of my parents had a Leading Edge 286 of some sort back in the day. I was still a young teen at the time and don't remember the exact model number, but that system does look familiar. They had the mouse and PC Paintbrush. Oooohhhh. I remember seeing the park program and asking what that was all about. Of course the one I really remember from my youth, due to it being advertised everywhere, is the Leading Edge Model D.

[@SuperHamsterGaming]

My first PC is a Leading Edge 386. As you might recall unfortunately it doesn't boot due to battery leakage. I hope to get it working eventually.

[@mofrak]

I worked in a new/used computer store back in the day and had a few of those cross my work bench, I know I had a manual for one in my collection, but that's long gone.

[@AntneeUK]

I see a Leading Edge machine and I'm immediately transported back to watching early Computer Chronicles episodes

[@johnscalia9451]

Back around 1986, I bought my first PC, a Mitsubishi Pc-AT which was essentially identical to yours with 1MB RAM and a 287 math co-processor. Now I recall mine used the grey floppy drives not the black ones. But the system was certainly fast. Mine is long gone, but I rather quickly moved onto DEC PDP-24 running BSD Unix.

[@pmatil1]

Interesting thing that the 2nd one said "only" 17 kg on the back label. The other two were 20 kg. Clearly they made it lighter as it's a newer model.

[@adriansdigitalbasement]

Indeed. I wonder if the older ones came with a full height drive and the newer one something lighter? Those big drives are quite heavy, easily 3kg

[@dannydoolhoff4215]

I suspect the lighter one had NO hard drive originally.

[@travispierce70]

Internally, this computer looks just like a Sperry PC/IT 286 that I have.

[@JVHShack]

Although, this comment isn't about this particular model, but it's somewhat related in the vein of the Leading Edge brand. I have a rather late Leading Edge PC (Fortiva 5900, aka "CPC-5200") and there's NO documentation on the particular model that I have. I found the manual for it's predecessor, a 486, but mine is a Socket 4 Pentium 60MHz. It seems like there's a common theme here, unfortunately. Maybe these particular models that are lacking their documentation (Adrian's 286s shown in this video and my Pentium 60) were the ones that didn't sell well? Were they flops like the Apple Lisa or IBM PCjr? 🤔 It was fantastic seeing you again in person, Adrian, (at VCF Midwest) and thanks for your input on my aforementioned Leading Edge PC!

[@mumblic]

22:10 Be aware that the 12 volt also dropped when you changed the 5v. That was probably the reason the 5 v was set higher

[@benbaselet2026]

I don't know how this particular one works but often only the 5V is really regulated and the 12 will just float higher or lower depending on the load on the 5V rail.

[@SteveSnow1]

Adrian, Leading Edge was a Boston (well, actually Canton) company and maybe there's a place to start if you want more in-depth info on these machines. Perhaps the Boston Computer Society hosted some talks about Leading Edge products and hopefully, this very model. Also, I seem to remember that maybe Businessland had maybe an inside track to Leading Edge (though I have no idea.) Still, it's interesting. Maybe the BIOS chips have some clue to the operation of the settings? Key, how about MIT or the MIT Magazine? Just fishing in the dark with a glo-worm...

[@andrasszabo7386]

I had one of these as a kid, starting with a 286 MB, then upgraded to 386, then Pentium, then got rid of the chassis. I used to install the bottom and top drives with only one rail, because none were available for sale here in Hungary.

[@qzorn4440]

I remember when the 286, 386, 486... several fellow workers kept stating on each gen., this all the computer that they will ever need. 😎 Thanks. 🤩

[@saifal-badri]

My favorite kind of video, awesome keep it up please

[@EShirako]

Re: 639kb vs 640kb base RAM in DOS; I think you mentioned "Scratch RAM" earlier in this video (I'm at the 58-ish minute mark as I write this) as a BIOS option. That being enabled can cause 639Kb, as can "XBDA" (Extended BIOS Data Areas) and a number of other "Turns out, we needed more RAM for operating system/BIOS parameters!" names too. Some newer systems with BIOS support for USB keyboards steal 1kish of RAM for that "EHCI" handoff or whatever of the acronyms that handoff was. Disable XBDA/Scratch RAM to get it back...though they normally only can do that by the old "Rob Peter to pay Paul" thing of stomping on higher software interrupt levels or something and using their RAM area instead. That 1kb might ALSO be for a 'Type 47' user-defined hard disk data area...depended on a lot of things. This all gave me a quick flashback to the "UMB=" and "DOS=" and "EMM386" and loadhi options to let your favorite DOS games run. I had a general use 'standard config.sys for most use cases', and a few drivers I could F8-step past if I knew I wanted to play a specific game. Some things were better in the "Good ol' days", but two things we DEFINITELY improved upon were "not needing to fight with my Config.Sys to make games be able to run" and "Fuel injectors instead of carburetors". Among many others, but those two have come to my mind today! Carburetors because I was recently behind someone's old Bronco that was from an era that used it and WOW do they stink! That exhaust is awful!

[@charlespaschal25]

The second floppy controller was probably added for use with an external tape drive which also used the DB37 connector.

[@XDymeStarX]

Leading edge, one name two computers. Thanks for the content Adrian.

[@DiskWizard001]

WOW ! I had CDC SCSI hard drive, probably 540Mb, long time ago. It was 5,25" full size the very same as one in video. Update from memory - CDC was later bought by Seagate.

[@YarisTex]

Hi Adrian. At 58:15 you say 639K for some reason. The reason is it will always be like this. First 64kb has space reserved for interrupt vectors for the CPU and BIOS. There’s small holes of memory in that space that get reserved for DOS but if I remember correctly you only get contiguous free memory space from 0000:0170h up to the last segment before the segment reserved for EGA/VGA at A000:0000

[@fnjesusfreak]

I suspect it's XTIDE.

[@KenjiUmino]

someone on youtube was able to get well over 640k of conventional memory - but for this to work, he could only use CGA or MDA cards that dont need A000

[@YarisTex]

@@KenjiUmino the person you are referring to is Jim Leonard, his channel is theoldskoolpc, he did it by patching the memory area where the BIOS stores the available conventional memory. Curiously that memory area is inside the reserved 1K that i talked about. I did it for myself by patching the BIOS. Both methods have advantages and disadvantages.

[@ChristopherIsene]

The CMOS/NVRAM lives on port 0x70 if remembering correctly, it is index based, I twiddled around with it a lot as school computers were locked down and floppy drives were disabled/unconfigured -- debug could run instructions to enable and then reboot, floppy enbled.

[@DiskWizard001]

Nice job, Adrian !

[@8antipode9]

I remember seeing these in stores, and drooled over them as a kid. We couldn't afford them so my dad built his own PC clone from mail order parts. I don't remember which models were available, but I definitely remember Leading Edge and their logo / case designs.

[@miketech1024]

Those self-test messages are very similar to the ones my Mitsubishi MP-286L laptop displays. Mitsubishi definitely had more than a little involvement in the production of these machines! Seems like this is a common thing for Mitsubishi. I have an ‘87 Dodge Ram 50 truck that is actually 100% manufactured by Mitsubishi (sold as a Mitsubishi Mighty Max). The only things actually made by Dodge are the emblems!

[@SockyNoob]

Mitsubishi electronics: Extremely well built, yet barely remembered. Mitsubishi cars: Built on a shoestring budget, yet fondly remembered.

[@RockwellAIM65]

Our Sperry PC-IT machines were shipped with EGA cards+Hercules Graphics boards, to ease development. VGA was just coming out but we were unsure they'd become a standard and EGA was really entrenched at the time. However, you could have gotten a VGA card if you were setting up a CAD system while these were being sold. An better alternative at the time was the TI Professional, which had a built-in voice-recognition option. The Compaq 286 Deskpro was nicer and had a 12 mhz option. The Sperry was kinda obsolete by the time it shipped..

[@50shadesofbeige88]

28:12 😂 thats why I love this channel. I'm glad I'm not the only one who gets excited over beep codes on a first boot.

[@soberjedi42]

Super cool seeing what looks to be the ultimate AT clone, at least if you want to run at AT speeds. Neat that you could switch between older and later AT speeds plus the slightly boosted one. Hoping you find a way to set up the MFM hard drive. If I ever tried to build a recreation of my 286, I’d need to have a working MFM drive in it. It just wouldn’t sound right without it.

[@oak_meadow9533]

Here in San Antonio, Texas I worked for a company that sold Leading Edge along with Xerox , Eagle, and Compaq. We never did very much business however.... I did learn programming.

[@bobblum5973]

I just started watching, wanted to say the the IBM 5170 PC/AT does have three half-height drive bays on the far right. The bottom one is not accessible with the cover on. We had one at work that I had to upgrade for Oracle 5.1 for DOS, and I had both 20 MB _and_ 30 MB full height drives in it along with the 1.2 MB 5.25-inch floppy drive in the top right bay. It took a 128 MB RAM card to get to 640K conventional memory, and an Intel 2 MB expansion ram card. It also had the Professional Graphics Adapter (PGA) card and display monitor and a Digital Equipment Corporation Ethernet card (DEPCA) using DECnet-DOS. I wish I had it today!

[@toddsilk8153]

My first PC was a Leading Edge model D so I have a soft spot for leading Edge computers. I even bought another one last year.still seems like a good machine for what it is.

[@JL-hy7ve]

I bought a pallet of those from Oregon state surplus in the mid 90s rock solid machines, I used one for several years for invoicing.

[@cnervip]

just started the video but just love the editing of the 1, 2... and a half

[@ultrametric9317]

That is one of the infamous Computer Memories Inc. HDDs such as were installed in the original IBM AT. We had a contract with IBM at my job (my first IT gig!) so we had an early model AT with the defective drive. We went through 3 of them!

[@2009numan]

great video Adrian

[@andypro]

My 286 was an Olivetti M 290 S that initially came with a 16Mhz CPU, no FPU, on-board VGA card, 1Mb of RAM, a 100MB IDE HDD, one 3 1/2" FDD and one 5 1/4" FDD. I supercharged it by adding a 287 FPU, 4 more MB of RAM to a total of 5. Added an ESS sound card and replaced the 5 /14" FDD with a CD-ROM drive for which I had to add an extra add-on IDE card. That was a pretty beefy 286 which I had used all throughout high school.

[@mrdjducky]

Closest I had was a Leading Edge Winpro 486, still looking for one as I remember upgrading that thing.

[@CarmonPerrin]

Brings back memories. Looks like a Sperry pc. The front bezel needs to come off to remove the drives. You can rotate the logo, as the case could be stood on its end. Good memories

[@JapanPop]

We had the VGA monitor from Leading Edge to match those huge boxes. I always admired those triangles in the logo. But never had a machine from them.

[@Peter_S_]

Adrian, I think you may have inspired a young Italian woman based on her channel's name of Sayaka's Digital Attic. I just had it suggested to me by the omnipotent algorithm and she did a DIY oscilloscope kit build and then used that to repair a C64. 👍👍👍

[@kitchentroll5868]

The FCC ID (bgb9j5mp-2400a) indicates that the system was manufactured by Mitsubishi Electric Corporation (US Division) circa 1985, although the mp-2400a variant was a re-certified variant of the original bgb9j5mp-2400 (no terminal a). The FFC records offer no details other than shielding requirements.

[@PCPSolutions]

Very nice, I have the Sperry version. Not much info on that either!

[@jecepede]

Aloha ! I have found this on a forum somewhere : SW1-4 and SW1-8 are to set three supported monitors: Monitor type SW1-4 SW1-8 Monochrome off off Medium-res color off on High-res color on on I have no way to test this but perhaps this is usefull to you. Cheeeeeeeeers Jecepede

[@patrickbateman3490]

Wow, gorgeous machine !!

[@apx5777]

That's great "what's better than 2..." thanks for making me smile Adrian 😀

[@joshpayne4015]

This computer is HONKIN' HUGE! Holy cow! Amazing. Didn't know that Leading Edge made 286-class machines. A bunch of years after I moved out, my parents, who were hopeless with technology, purchased a Leading Edge Model D at the time when 386's were basically the standard - the D computers were being closed out and were not really that useful, esp. since theirs was a monochrome model with dual floppies. I think they may have turned it on once or twice but it just sat there gathering dust until they donated it years later. It was a solid little machine, just a basic XT-class computer without any real differentiating factors as I recall.

[@evaDrepuS]

Nothing on pin one... Pin two is binding... Oh wait, wrong channel...

[@nervenderkobold2861]

Or you mean the KeyLockSmith?😅

[@jowi_24seven43]

For those confused, the cylinders, sectors, etc to put into the CMOS/BIOS if the HDD was not auto detected, was printed on a sticker on the HDD so no guessing was needed. It was general knowledge for any PC user.

[@ZomB1986]

25:26 That "non-standard" connector is just a run-off-the-mill JST connector. It's their most common series too, PH.

[@NoPegs]

Switch 7 possibly DVORAK instead of QWERTY?

[@InfiniteBrain]

I think another possibility with the Compaticard might be that it can run 8" drives? Can't remember for sure but I looked for a solution quite a while ago and it seems like that was a card that could do it.

[@nervenderkobold2861]

Tried from "VOGONS Vintage Driver Library" Category: Motherboards Mitsubishi MP 286L laptop, MP 386s and MP 386/25 desktop Utilities Disk 1989 ???

[@AlexBuB]

It Look right

[@teekay_1]

I worked with a Leading Edge, Model D with an 8086 processor, and I recall this model was anticipated for a long time, and by time it came out, a lot more low-cost clones were available with the 80286, so it's effect was nothing like the Model D

[@ocsrc]

There are lots of lost PCs There was an ISA PCI motherboard that was I think a 486 or a 586 CPU and it was THE board of a year right around 1995 Literally EVERY PC I bought had this identical board and it was silk screened the names of the different sellers but it was the exact same board. It was a massive pain in my head for years because the board didn't support the larger hard drives. It had an auto detect hard drive in the BIOS but I believe it couldn't detect above 500 MB or maybe it was 300 MB I remember trying to flash the BIOS and the last version they made didn't detect the newer larger drives. I even tried hot swapping and flashing a blank eeprom with a hacked BIOS and it still didn't detect the larger drive. Basically people had these boards and they were Windows 3.1 or dos and they had four slots for Simm memory, and the machines came with I think and 80 MB or 60 MB hard drive. When I upgraded them to Windows and put the install files in a Win95 directory and installed Windows 95 and the software programs there wasn't any space left, so I would get a call from the company within a short time and I figured I could just install a new hard drive. But the BIOS was never designed to work with larger drives and for whatever reason it wouldn't accept a bootloader program to bypass the BIOS. I got so sick of seeing that board and I don't know how or why but there must have been one factory in Taiwan that just cranked out hundreds of thousands if not millions of this board and everyone bought it from them and they silkscreened the names of the company or no name at all. Some of them had no name, no model number. A lot of the homemade machines where people bought the motherboard from a mail order in PC magazines sold this board. It was so frustrating because I had older 486 and even 386 machines that the BIOS was able to detect large drives even in the low GB sizes and this newer board could not. Really had a tough time with it. Just very stressful The problems from the early days people just don't know what it was like.

[@miscbits6399]

It was probably PC Chips or Microstar international (MSI) - both makers did this. Usually there was an identifying code in 2-3mm high lettering between the 4th and 5th slot which enabled working out the spec. These models were infamous for "fake cache" (dummy ICs in the cache ram sockets and a hacked bios reporting cache installed) that would manifest in Linux as a seg11 fault during kernel compilation - mostly of PC Chips origin, but some MSI boards too The New Zealand importer of these boards was heavily fined by the Ministry of Commerce for deliberately and fraudulently misrepresenting the boards - a company rep then got on Usenet's nz.* groups and claimed "it was all a mistake". Upon seeing this reported via Computerworld magazine the Ministry issued a second - tripled - fine, for further attempts to deceive buyers and ordered the company recall, destroy & replace or refund (at original sale price) all affected boards, overseeing the destruction (These boards could have been salvaged and losses minimised by fitting a non-hacked BIOS, but the MoC was determined to make them HURT)

[@thomas-i5o7h]

I've never seen or heard of Leading Edge.

[@onyourjackjones]

This came out just after I was born! 🥺❤️❤️❤️❤️

[@MichaelRusso]

I remember the 90's when the Leading Edge computers were everywhere, at least where I lived. Now they are hard to find.

[@DefaultFlame]

Very interesting and a remarkably good machine.

[@chubbyadler3276]

49:00 Last check I had, the 80286 had a bug that cause the 384K extended memory block to become inaccessible, so that may be the nature of the beast. Then again, I've not looked hard into that behavior. All my 80286 machines that I had have had 640K.