IBM PC on steroids : 5161 Expansion Unit

[@MichaelAStanhope]

IBM didn't even offer this until the PC XT was well into development. They knew customers who just dumped thousands on a PC just to learn that the next model was more expandable and offered a hard drive would be pissed. So the 5161 came out. It is a PC XT case to the exact dot, even uses the XT's power supply which is beefier to run the hard drive. You can install 2 drives in the expansion chassis, but that was rare since that 10mb drive was over a $1000 option at the time. With the expansion unit, and the base PC, you essentially had an XT on steriods since you actually had more expansion than an XT having 2 hard drives, and 13 expansion slots. Since the processor was the same between the PC and XT, in many ways, this was a better choice over buying a new XT.

[@ThunderClawShocktrix]

even when you factor out the 2 lost slows for the connectors cards you still have 11 slots thats 3 more than an XT and 4 more than most full ATX boards today

[@ropersonline]

Don't forget to sell those defective RAM chips to Clive Sinclair at a steep discount.

[@andyhu9542]

haha that's a good one!

[@piecaruso97]

The expansion unit case is basically an ibm 5160's case

[@RetroSpector78]

Indeed it is. Thought I mentioned it in the video but apparently I didn’t :) thx for pointing it out.

[@GuybrushThriftweed]

And they even used it for the 5162 :p

[@djpirtu2]

That hard drive gives me memories. Back in 80's we had 286 clone, MDA, and one HD floppy drive. Later we got CGA/HGC and 40Mb Seagate MFM -drive. That drive broke quite fast and then we got from somewhere the same 10Mb hard drive as in the video. So small... Remember watching that stepping motor on the side while using it.

[@parrottm76262]

My old company was always excellent at buying me the computing tools I needed to do my job, but I could never get them to get me the expansion unit. I am so jealous!

[@GuybrushThriftweed]

The seller told me the combo was found stored in the attic of the office where his mom worked. They were clearing it out. Guess this company had taste :p Explains the content on the HD too probably...

[@adamsfusion]

This is one of the reasons I love computers from this era: Simplicity. That card and expansion unit are literally nothing more than ISA links from one computer to another. You could have fashioned a cable with ISA card edges on both ends and plugged them into both and you'd get more or less the same effect, maybe with a bit of clock skew.

[@Agamemnon2]

Ah, I was wondering about that.

[@bdbensley]

i used to work in ComputerLand where we sold these expansion units. I think I sold two of them total. I think the store actually sold three total. Two went to the local university.

[@RetroSpector78]

Haha ... love hearing stories like that ! Sometimes difficult to understand how popular things were or how people used them. i can imagine the 3 free expansion slots in the 5150 were limited. If you wanted some more ram, a harddrive, a mouse I can imagine things got full very quickly.

[@GuybrushThriftweed]

I wonder how much it would cost nowadays, inflation taken into account Indeed nice to know this extra info!

[@Zankuho]

7:25 there's even a Zilog Z80!

[@RetroSpector78]

Nice catch :) .... I think you’ll find z80 chips in more devices than you can possibly imagine ...

[@lelandclayton5462]

The System's CPU can't cope with running the Hard Drive by it's self so it passes the information to another CPU typically on the Controller and at times on the Hard Drive's main circuit board would have one. This is why Hard Drives were so expensive.

[@AndreiNeacsu]

@5:00 You only get 6, not 7, additional slots. Just count the total empty slots before and after if you don't believe me, or take into account that there are 2 ISA cards that need to be installed across both units and subtract them from 8.

[@RetroSpector78]

Thx for the math lesson. And yes I do believe you :) honest slip of the tongue.

[@AndreiNeacsu]

@@RetroSpector78 Thanks for your awesome videos!

[@AdamChristensen]

Cool! Good to know there are homebrew clone cards as well!

[@RetroSpector78]

Yeah there was talk about it a couple of years ago. Also didn’t know they materialised. Indeed good to know

[@Wingnut353]

@@RetroSpector78 You can also use those cards with other backplanes also.

[@UmVtCg]

I'm so happy channels like this exist. Back then I always wanted a better CPU, more RAM, more storage space, a graphics excellerator, games that look and play like today's games, virtual reality and a holodeck. Thanks to channels like LGR, 8 bit guy and RetroSpector78 there is no need for me to own this kind old hardware, I get my nostalgic fix by watching these vids (and owning a mini SNES) and then comfortably endulge in the things I've always wanted since I first powered on my old Laser 310 color computer, today's tech. Well, exepet for the holodeck that is.

[@GuybrushThriftweed]

TBH having some of the hardware is nice too :) not that you do much with it :)

[@RetroSpector78]

Feels a bit strange seeing my channel name (albeit slightly misspelled) next to LGR and 8 bit guy :) But thanks a lot ... glad you enjoy the show !

[@DavidWonn]

To an extent, you can play on some virtual PCs via pcjs.org in your browser. (I personally like the Windows 3.0 option on my iPad.) But in the end, nothing beats physically having some old hardware around to tinker with.

[@UmVtCg]

@@RetroSpector78 I love your channel, keep it up. Anyway, I corrected my mistake, the forgotten "r". When sitting next to LGR and the 8-bit guy it certainly deserves correct spelling.

[@RetroSpector78]

WaxP3 haha ... thx a lot ! :)

[@johnm1133]

Mooie set! Ik heb veel met IBM PC's gewerkt, maar deze expansion unit heb ik nog nooit gezien.

[@RetroSpector78]

Ja ... uniek stuk ... jammer genoeg is deze niet van mij (gelukkig wel alle andere IBMs), maar leuk om eens mee te spelen... grootste externe hd tot nog toe :)

[@silvio4027]

Thank you for this Video. I have the same setup with the same hard drive in the expansion unit. It special to me because it has a prototype communication card with software designed to assist deaf children. It's been sitting in the closet for 25+ years and now I'm trying to bring it back to life. Unfortunately, it posting an 1801 with the expansion unit attached and, without the expansion unit, if fails to boot from the floppy. I tried swap the floppy drives (and changed the Jumper) but they all boot into Basic. I also watched your video on fixing a Tandon drive which will be the next think I will try. Again, thanks for the videos.

[@TheNightOcean]

Great video ! By the way, if you wan to backup old MSDOS computers with comfort, you can use FastLynx 3. It uses Parellel/Serial/USB ports (I use an USB to Serial adapter) , runs within a nice GUI on Windows Seven (never tried W10, but maybe it works), and the MSDOS Client is able to install itself just by using the function "Upload DOS Slave" and MODE/CCTY commands on the MSDOS PC side. Very usefull, powerfull and easy to use, it allows your modern PC to acces all drives of your old MSDOS PC.

[@RetroSpector78]

Thx for the tip will check it out ... I’ve always got a “new” retro machine standby that can boot into msdos to start interlnk. Then I boot into win xp and take it on a usb thumb drive.

[@paco3523]

You mean you can install software on another PC by serial/parallel?

[@JimLeonard]

Welcome to the 5161 club! For a silly challenge, try to fill it on a 5160 -- 14 total slots with each card working. (It is possible, I've done it, you have to use many cards that don't need an irq)

[@RetroSpector78]

That was kinda the plan ... was going to make it “easy” on me by just doing it with the 5150 but you raised the bar for me sir :)

[@GuybrushThriftweed]

And he can leave the cards in when I get it back :p

[@JimLeonard]

@@RetroSpector78 I don't know if it is considered cheating, but I have a few sound cards that are fairly rare and unique and that's one of the ways I got all 14 slots full and working. Other cards include EMS, networking, both MDA and CGA, a joystick card (I did NOT put a sound blaster in), and extra parallel and serial Potts. You can put in an scc-1, adlib, and CMS sound cards instead of a sound blaster, for example. Good luck!

[@RetroSpector78]

Jim Leonard got some exotic cards as well like prototyping boards , analog - digital converters .... will see what I can find :)

[@DxDeksor]

Now get a IBM CGA monitor and put a CGA card in your pc and use each case as a stand for each monitor for a dual monitor setup :D

[@lawsonott3]

ok. but could you keep added expansion units into the previous expansion unit? if so, to what end?

[@absalomdraconis]

I have wondered about that too, but I suspect that either there would be signal reflection issues, or you'd simply run out of address space.

[@dave4shmups]

Fantastic video! Thanks for sharing!

[@RetroSpector78]

dave4shmups you are very welcome !

[@lelandclayton5462]

A simple way to breakout the Address Bus and Data Bus. I bought one of those from a Flea Market not thinking it was a Expand unit. Was just the Backplain, Power Supply, Cable, Transmitter and Receiver cards. Surprisingly it worked on my 386 but you had to turn the PC and Expander on at the exact same time or the Video would be garbled and would hang on post. Had my dad build me a junction box that was nothing more then a double gang Electrical box with a Light Switch and two Outlets with an Extension cable. This way I could switch the PC and Expander on the same time. Use the Expander to host all of my 8 bit cards and two SCSI drives. Had it for a couple of years until the Power Supply died and I retired it. Later on I reused the Case for a 486 build.

[@angieandretti]

That's really cool. I was about to ask if you could theoretically use this with a newer PC that still had ISA. Sounds like you could!

[@RetroSpector78]

On my XT clone it doesn’t seem to work. With the cable connected the XT clone just sits waiting on boot (blinking underscore). No disk drive initialization. With extender card but without cable attached the XT clone starts again.

[@absalomdraconis]

@@RetroSpector78 : Might be a timing issue. See if your clone has a higher clock speed.

[@Stoney3K]

Looks like the 5161 was just an empty XT chassis which only carries a dumb ISA backplane board and a different badge on the front. Which would have been quite easy for IBM to manufacture since they already had almost all of the bits. The extender/receiver cards are just ISA bus transceivers so the bus can go on a cable. Was it possible to connect more than 1 expansion unit so you could build a massive rack?

[@bpoolxantx15]

Wow...... love it...great units when combined....👍👍👍

[@osgrov]

This is extremely cool. I had no idea these existed. :) Great video, great topic - you've earned a new subscriber!

[@RetroSpector78]

Really glad to have you onboard ! Thx for the sub and looking forward to hearing your feedback on the current and future videos. Have a great day !

[@Inject0r]

This. Is. AWESOME!

[@RetroSpector78]

Haha ... glad you liked it.

[@greggv8]

Before replacing the RAM chip I would have pulled it then put it back in, along with pressing down on all the rest of the RAM and other socketed chips. The first stage in troubleshooting a PC or clone in the DIP era was to give all the socketed chips a push down to re-seat them and cut oxidization that could be causing resistance or total insulation of a pin. If that didn't fix the problem, remove and reinstall all the socketed chips. I fixed many computers doing nothing more. The cheap leaf spring contact sockets used by IBM and most clone manufacturers for DIP chips back then would have the chips slowly rise up over time. The more power cycles, heating and cooling, the sooner the chips would pop up. Though never to the extent of the apple ///, which ran extra hot and apparently used the cheapest, weakest sockets available. For the price of the thing it should have used machined pin sockets. It was nice to see a board with those, because it almost certainly wouldn't be any oxidized pins causing the problem. I'd still push on all the chips and listen for the telltale *crack* of a chip seating better.

[@RetroSpector78]

hehe ... the telltale crack .... indeed. I actually did that off-camera but the problem persisted, but definitely worth a mention so I appreciate the comment ! The PC is sometimes throwing PARITY CHECK 1 after POST, and occasionally flags a 201 memory error in bank 0 (the chips that are soldered onto the board) during POST.. If I insert a 384kb memory expansion card (that works in another 5150) it only runs stable if I configure the PC with 574kb of RAM. Anything higher than that and the PC hangs on boot... So I do suspect there are still some memory issues with the PC.

[@deepspacepilots]

Just got one today at an estate sale!

[@douro20]

I remember getting parts of several 5150s and 5160s from my old high school, and they had cables and cards for an expansion unit but I don't remember an expansion unit being present.

[@ClanTeamKill3r]

this is really interesting, something I did not know existed, great video

[@RetroSpector78]

Glad you enjoyed it !

[@RWL2012]

I didn't know this existed either! I'd love to see the PC, expansion unit and that dual monitor setup arranged to look like 2 PCs!

[@RetroSpector78]

Someone did challenge me to setup an IBM PC XT with the expansion unit to have a total of 14 expansion cards :) so you might end up getting what you wish for :)

[@hikaru-live]

I somehow feel the need to build a modernized thin cable expansion card. Said modern card would serialize the 68-pin interface and send things over a single USB 3.0 connector (not USB protocol, just the connector) using a modern 1.25Gbps serdes interface.

[@BollingHolt]

Yeah, it seems that these old MFM hard drives are still working when their 3 1/2 inch counterparts are not! In the early to mid 1990s I never would have guessed that to be the case in 2020!

[@davidallen9257]

I've got two 286es, one with its original 1990ish hard drive and the other with one installed in 8/1992. Both 3.5" IDE. Get Western Digital or Seagate. Quantum ones hold their own pretty well too.

[@thebiggerbyte5991]

Is the backplane board available also? I have a spare 5160 chassis I could convert... Great video - I learned a lot.

[@RetroSpector78]

Thx ! Github project doesn’t mention it, but they do say that there were a couple of commercially available passive isa backplanes back in the day (and still being sold perhaps somewhere).

[@thebiggerbyte5991]

@@RetroSpector78 Interesting. It seems like the missing piece of the puzzle, though being just a backplane I doubt it would be difficult to reproduce. Thanks for the info!

[@RetroSpector78]

Would make for a nice weekend(s) project :)

[@Wingnut353]

Sergei malinov's ISA backplane would probably work, dunno if his ATX power off logic would interfere. Also there is Advantech's PCA-6108 which you can find online for $40-100 with 8 slots. They make a 20 slot backplane also but I dunno if that would work as it is muitisegment.

[@bigdrew565]

My neighbor had one of these. He worked for IBM he managed to kludge some hardware and software together to make a monster 3270 PC so he could do most of his work from home. There was a point where he was on a team trying to make cartridge ports of some popular PC and C64 games for the PCjr. They disbanded his team, but a lot of the work they did was still on the mainframe. Which wound up on self booting diskettes being played on my Tandy. Nobody was buying the 5162, so it got given to employees. They always forced the employees to take the shit the customers didn't want. It was the same with the PCjr.

[@pparadigm]

Many thanks, I've not seen one of these units.

[@woodenotaku]

Would this be compatible with other IBM PC-compatible computers? Or is there something special about the PC AT that makes it work?

[@RetroSpector78]

It will only work with 8088 based xt’s. 5150 / 5160 should work, and if it doesn’t a bios change can fix it. I think it would probably also work with xt clones. Don’t think there is anything IBM specific. Will give it a try and let you know.

[@LowSpecActionSquad]

@@RetroSpector78 Please do! That would be super awesome if it did!

[@lelandclayton5462]

I had it working on a IBM-Clone 386 that had a Biostar Mainboard and a MrBIOS. but I had to turn them both on at the exact same time. If the Expander was on first it would try and send low voltage signals to the Main PC Bus and if you tried to turn on the Main PC afterwards the Power Supply would kick on for a second then kick off. If you switched the Main PC on then the Expander the Video would be garbled and hang on Post.

[@juanschroder6519]

0:00 holy cow!!!!!! look that boards in the shell!!!!!

[@andydelle4509]

Dynamic RAM, especially chips from the early 1980s do deteriorate from natural background radiation.

[@thomaseboland8701]

Before replacing the chips, reseat the questionable memory. Often just a touch of corrosion on the pins, that gets wiped away on removal and reinsertion. It certainly was true back when they were newer for sure. At the time memory was hugely expensive, so doing this check was worth the time and effort. Now maybe not so much if you have lots of spares that cost you next to nothing.

[@nneeerrrd]

@@thomaseboland8701 this ☝️

[@leisergeist]

There were eventually "HardCards" for the PC line, but they took up *two* precious ISA slots lol They're way more recent though: from the late 80s, well into the PS/2 days. Meant for keeping people's old expensive hardware alive, same as 286 upgrade cards :) A hard drive mounted on an ISA card is pretty neat!

[@raulcortes937]

It really works "out of the box".

[@rancidbeef582]

I've got an expansion unit. I don't have an original PC, though. I *think* the extender and receiver cards on mine were just linked by a ribbon cable, though.

[@aurathedraak7909]

LGR would gasm, to this

[@Wingnut353]

Computer reset had a big pile of them... I got 3. And there were still more there when I left. I also made had sender cards made and am buying the ICs to build them now. anyway he has been to CR I'm not sure how he could miss them if he wanted one. Also the sender and receiver cards can work with any passive ISA backplane from what I remember reading so you don't' actually need an IBM card you just need to make the 3 boards.

[@GuybrushThriftweed]

@@Wingnut353 Oh I wish I could have visited that shop....

[@nneeerrrd]

nah, he's busy with another Sims review 😁

[@OmegaEnvych]

Yep, I can't wait for upgrading this with all the expansions. Is it possible to install 3.5 floppy disk drive to this machine? I wonder.

[@marzsit9833]

yes, 8-bit high density floppy controllers do exist.

[@Romanon26]

Nice setup, I have also one. What is your extender card switch configuration?

[@RetroSpector78]

Haven’t really looked at it yet. Focus was just getting it up and running now. Will go into more detail on it in the next video when I start filling it up with expansion cards. Great that you have one. Mine is a loaner, but great fun playing around with it and learning about it.

[@mrvellu]

what a beast!

[@5argetech56]

Oh oh,,, Oh my GOD!!!! 8 bit expansion bus..

[@pcwizard7Tech]

With that height gain from the extension unit, I would move them to right and have the monitor on the desk by itself

[@RetroSpector78]

Next video will add a cga card + monitor so they will sit alongside each other. Stay tuned for that.

[@GuybrushThriftweed]

Ain't that a nice view!!!

[@RetroSpector78]

It sure is :) thx again !

[@GuybrushThriftweed]

@@RetroSpector78 No problem :)) Thanks for the troubleshooting and letting this quite rare bird (it seems) shine! Looking forward to part 2. You can leave all those cards in then if you want haha.

[@only257]

Cool😊

[@idahofur]

I would say good job on finding the expansion case. But it is loaned to you. This is why I had to tell myself over and over again. Don't keep collecting things. I just got a apple ii plus and dying to max it out. On the other hand my pocket book is saying noooooooo.

[@Kennephone]

I wonder if you could take an isa single board computer and use the expansion unit on it's own.

[@erin19030]

Talk about a boat anchor. IBM sure hosed a lot of people.

[@ropersonline]

Seeing the 5161 stacked on top of the 5150 bothers me somehow, b/c of ergonomics. Also, the 5150 is dual- or even triple-monitor capable (MDA+CGA, the latter possibly driving both an RGBI and a composite/TV monitor). If this were mine, I'd put the units side by side, and then I'd put a little shelf above, on which I'd have 5151 and 5153 monitors sitting pretty, along with a (preferably period) colour TV/composite display. Well, in my dreams.

[@RetroSpector78]

ropersonline hehe ... I have posted a video showing the IBM pc in a dual monitor setup like you mentioned. (Cga and mda). Part 2 of this series will include the setup you mentioned (dual, not tripple)

[@ropersonline]

@@RetroSpector78 Thank you; I've just seen that. I left a comment there for you too about the Guide to Operations. If you might be able to speak to that, I'd be very grateful. :) PS: If you could try a triple-monitor setup, you could probably run 8088MPH... Then again, I don't actually know if the whole PAL/SECAM/NTSC thing might present a compatibility issue with that?

[@ropersonline]

@@RetroSpector78 PS: In case you get a chance to look at it, this is what I wrote over there: kzbin.info/www/bejne/aqvYmI19d7WHiaM&lc=UgwBcrFbNSty-EU3Jp54AaABAg I would be really interested in hearing if you know anything about that.

[@Caseytify]

One wonders if you can plug the receiver card into an XT and have it work?

[@AlejandroRodolfoMendez]

Wow really cool and a nice piece of tech. Still it was expensive then. Basically it's a rizer card like in the IBM ps1 and ps2 systems but with parity check.

[@dangingerich2559]

The first version of Thunderbolt, then?

[@AlejandroRodolfoMendez]

Where do you get the ram chips?

[@Superchad245]

in theory would this work with an XT as well?

[@rwdplz1]

"Something you don't see everyday" I have one I literally see everyday, it's right over there. I don't have that original cable though, I bought that Mouser-sourced replacement. Mine has two hard drives, I've never seen that blank panel yours has?

[@RetroSpector78]

You’re on of a lucky few I think ... not many of those around in working condition I’ve been told.

[@GuybrushThriftweed]

Consider yourself lucky then :) I had never seen one over here TBH

[@OmegaEnvych]

You're one of the few people, who has one, true, so cheers to a lucky person!

[@GuybrushThriftweed]

@@OmegaEnvych According to a site, there are around 20 fully working ones but I don't know if that it correct

[@OmegaEnvych]

@@GuybrushThriftweed you know, this is actually even more surprising. I mean, ok, I never seen one, but I thought that there would be at least couple of thousands of these units. Or at least several hundreds, not under one hundred.

[@CCfiftyeight]

Interesting systemupgrade. 😲 I think The old Computers of The 70s, 80s and early 90s are much more fascinating than modern ones. Your PC ist a German one? TÜV and GS?

[@AlyxxTheRat]

I think we take for granted how compact computers have gotten.

[@nickwallette6201]

Those are MOS chips alright! Dropping like flies...

[@RetroSpector78]

Yeah ... getting random memory errors from time to time (either during post or when the machine is running In certain apps)

[@PicaDelphon]

I would retest those ram chips, could of been a fault on the Dip Sockets..

[@JenniferinIllinois]

Holy cow, that 62pin connector could be used to connect a couple IBM mainframes together. It's bulky and then some!!!! Hehehe...

[@KonuralpBalcik]

why not install IBM Dos ?

[@brentboswell1294]

The difference between MS-DOS and PC-DOS, back in the day, was literally, BASIC... PC-DOS interfaced with the BASIC interpreter that was built into the ROM on a genuine IBM machine, whereas MS-DOS replaced any calls to BASIC to GW-BASIC (An executable on the MS-DOS boot disk).

[@skonkfactory]

To be fair, it only gave you six additional slots total, since you lost one in the PC and one on the expansion backplane.

[@jim8230]

I'm guessing the cable plugs and receptacles were made by AMP...

[@Darknecros7]

I wonder if some people loaded this expansion unit with dual hard drives?

[@booboo699254]

Yes of course. But was expensive....

[@paco3523]

Not sure if the power supply would like that

[@wolfrobots118]

computers of that time were like trucks

[@AiOinc1]

See now you need to have a PGC card and monitor to get a triple monitor setup. Get a true badass XT setup going. Maybe a 286 upgrade board and run Windows 3.0

[@knappe3223]

New subscriber here, nice work!

[@RetroSpector78]

Thx a lot ! Appreciate it.

[@matthew65536]

Is there something wrong with your monitor? The text appears very squished.

[@JohnLobbanCreative]

I have a working XT and Expansion Unit.

[@Kundalini12]

There is a 5161 on eBay as I write this, it's looking a bit rough though.

[@Wingnut353]

They aren't that rare after all.... just not as well known. Also it's just a passive backplaen so can be cheaply replicated if you want with 3rd party hardware. Especially since there are open source sender receiver cards now.

[@joe72205]

Please use a static-safe workspace so these old artifacts are not damaged!

[@adityar981]

Yay

[@deanc4505]

But Can It Run Crysis?

[@Synthematix]

And yet a raspberry pi is over 3 times faster.

[@HikikomoriDev]

Man.. Imagine the dudes and engineers who had this at the time.. they where probably filthy rich cause they could process or multiply their computing time and power to get client work done on the fly...

[@bobblum5973]

Wow, I haven't seen one of these in decades! I think there were third-party expansion units for the XT and AT, again mainly to add more slots. With the advent of multifunction cards the need for extreme numbers of slots dwindled, so the expansion box market went away. I seem to recall a unit to add an S-100 expansion chassis onto an Apple ][, but I'm sure that wasn't a big seller.

[@TeslaTales59]

I'll bet those are not too quiet and use lots of watts!

[@Vatharian]

This idea lives now, as a PCI-Express backplane. Recently abused to the extreme by cryptocurrency mining businesses. I wasn't expecting such a thing existed for 8-bit bus!

[@RetroSpector78]

Did not know that ... nice to see we can learn from each other ! :)

[@intel386DX]

heeh crazy but cool! :D

[@spidermcgavenport8767]

I thought at first glance that was a LFH-60.

[@ЏонМастерман]

We've sped up technological advancement so much that this thing looks like it came from 50s instead of 80s.

[@zerogravitygamin3429]

This is how you plug in to the matrix

[@erin19030]

$2000 for that 10 Mb HD

[@raspoutine7241]

Parity check 😐🖐

[@soviet9922]

your monitor look terrible squashed adjust it for god sake :D

[@nowheremanjk8624]

clear the screen better