Rare 486 interposer repair & IBM PS/2 Model 57SLC restoration (8557 & SLC2)

[@Epictronics1]

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[@datPinto]

Pretty soon you'll have enough classic IBM's for a museum! Love it.

[@IBM_Museum]

Hey now! 😉

[@datPinto]

@@IBM_Museum 😁

[@TheUAoB]

I dropped an AMD FX8370E and the pins looked like that. I straightened them all out using a tiny crosshead screwdriver by touch, since my eyesight isn't good enough anymore! It did take a while. It's still working!. :-)

[@DavidSaulesco]

13:56 Very satisfyingly rhythmic supercut of the desoldering gun! As a musician, I approve 😎

[@wacholder5690]

33:20 Ask around for the grey "vertical stand" for these 5-slot cases. I wonder if I still have one in stock. But I may have a blank or CD-ROM bezel. Leave me a note and I work my way through the boxes in the basement ... 🙂 You'd put yours in the false way. The vertical stand mounts at the side adjacent the PSU. Power button is in hand reach from a desk then.

[@Epictronics1]

I'd love to find one of those vertical stands. They look great

[@MySmartHomeDomain]

That would be nice to see it with a stand and a cd-rom eventually. Maybe even search for ultimedia parts in the future? Hope you do have them for @epictronics1 though

[@detalite]

27:25 Many pre 486 motherboards struggle with suport for non standard RAM size like 2, 8, 32 MB. Sometimes RAM IC have non symetrical RAS/CAS adress lines, what is causing most of the problems with compatibility.

[@cbmeeks]

You should paint that power button red. 🙂

[@Epictronics1]

Maybe I can have red switches printed?

[@RinoaL]

I personally would have just straightened the interposer and replaced any pins that were gone, but that's interesting that you fully replaced it.

[@Cyberdeamon]

Ye, I've seen people straighten them with mechanical pencils and sewing needles with a ton of patience before.

[@blakecasimir]

Excellent work restoring that interposer, and this classic lesser-known IBM system.

[@Epictronics1]

Thanks!

[@RetroTechChris]

Fantastic! What a great repair there. My Model 70 386 has an interposer upgrade too. Pretty rare upgrade!

[@Epictronics1]

Thanks! Cool, is it some sort of SLC board too?

[@RetroTechChris]

@@Epictronics1 I think it is actually an Intel CPU, 486DX 33MHz . It's a Kingston 486/Now!

[@Epictronics1]

@@RetroTechChris Sweet. I need to find one of those too :)

[@stephenkennedy6358]

I love the build quality of this case, my Model 77 486 DX2 shares the same case and 2.88 floppy drive. The performance is top notch along with the price back in the day.

[@jerther_]

Really nice and clean job on that array of pins on the interposer!

[@Epictronics1]

Thanks!

[@craigrenwick9132]

Really nicely done repair and restoration. Looking forward to your remaining repairs/updated/uprades. Thank you for all your work

[@Epictronics1]

Thanks!

[@BigBadBench]

Even I cringed when you brought out the dremel wheel! Very interesting machine and interposer!

[@Epictronics1]

You're right, the Dremel is more suitable for rare power supplies ;)

[@spokehedz]

Ahh, the 2.88mb floppies. The bane of my existence. Someone got bamboozled by the local IBM rep for my local branch of Library, and they used them... And it always caused problems when those disks never worked anywhere else. Save your work at the library, but bring your own disks.

[@TruckFan542]

This was an amazing video. Loved the chat interaction- the moos were extra fun, and this channel just has an awesome community.

[@Epictronics1]

Thanks! I agree, the chat is fun :)

[@drewnewby]

Now I wait 30 minutes, fooled again to click. Must wait to see which interposer you have this time.

[@Epictronics1]

I need to give everyone time to grab some coffee before the premiere :)

[@drewnewby]

Interposers must make poor hammers, all those wood chips.

[@Epictronics1]

@@drewnewby That explains it! ;)

[@wacholder5690]

5:53 - IBM PS/2 was a large construction kit. The same base chassis had been used for an ISA Model (8540) as well as for the 9577's and - IIRC - an entry level RS-6000 of which I cannot recall the model number, cause we did sell and support PS/2 only. A rare find were an IBM PS/2 Ultimedia M57. I have a 9577 with the Ultimedia stuff. Used it in the early 90's along with the ACPA/A to convert analog records to MP3 ...

[@bobbobson1605]

I stumbled across a plain 57 486SLC2 a few years ago and bought an M-ACPA/A card to get as close as I could to the Ultimedia configuration. One interesting thing it has in its driver/documentation diskettes is C source code for doing various things with the big Ti TMS320 DSP chip, including a JPEG decoder.

[@wacholder5690]

@@bobbobson1605 The TMS320 was a family of chips assisting for compression purposes mainly for audio but video as well. Given the time they appeared they were pretty groundbreaking and the developers added a lot tools - of which the MPEG audio coding was the most prominent. I had a 77i / 486DX2-50 with the M-ACPA to record my old analog records under PC-DOS 5 and using the M-ACPA kit for quite some time. The bottleneck was the harddisk, since that was generic SCSI and they were non-streaming capable. Once they *had* to recalibrate your record was losed up. I recall having recorded the first side of Pink Floyds "Dark Side Of The Moon" at least three times ....

[@Choralone422]

Great repair! I was so glad the interposer could be saved!

[@Epictronics1]

Thanks!

[@MySmartHomeDomain]

Nice video. I got a new old stock cpu upgrade that you used. It has that bracket you used and also had a black square plastic spacer that sits around the 387sx socket. The 56/57/76/77 chassis all had rotating badges, just like the pc 330's. The 76/77 also had floor stands that clipped on the case.

[@Epictronics1]

I'd love to find one of those stands, they look cool

[@jozsefizsak]

That was very satisfying! I was worried about those bent metal tabs being work hardened and cracking during straightening but it seems the IBM gods were smiling on you that day.😊

[@Epictronics1]

There might have been some luck involved :)

[@LotoTheHero]

That's really awesome that you were able to save that interposer! :D

[@awilliams1701]

I'm actually surprised the 2.88 drive never caught on. I wanted one. So did everyone I know, but you couldn't find them.

[@Epictronics1]

It is strange indeed. Especially sins they were backward compatible with regular 1.44

[@LotoTheHero]

@@Epictronics1 A couple things: in the above sentence the word you want is since instead of sins. At 2:30 I believe the expression you are looking for is "It never really took off." not "on". Just a few things to be aware of. **Edit** You probably mixed up the expression "It never really took off" with "It never really caught on". In regards to the 2.88 MB drive, I don't really remember them being a thing. Since they are backwards compatible, I wonder why they didn't take off either. Maybe it was a cost thing?

[@pedrocx486]

@@LotoTheHero do you really need to come here just to be annoying about grammar?

[@LotoTheHero]

@@pedrocx486 I wasn't trying to be annoying, I was trying to be helpful. I'd want someone to correct me in the same situation if I was speaking in a second language.

[@Epictronics1]

@@LotoTheHero Thanks, I appreciate the help in spotting my mistakes. I'll try to remember

[@piwex69]

About the double sided ram not being correctly recognized- it might be the case of the bios upgrade. I remember once we visited the bank branch where they used Compaq’s desktops. After running over with bios upgrade disk, each of the PCs started to report twice as much ram as before. It had appeared they were fitted with double sided sticks which started to be recognizable.

[@jasmijndekkers]

Hi Epictronics, Great job again and nice to see you work on a IBM. Greetings from Steven from the Netherlands

[@Epictronics1]

Thanks :)

[@IBM_Museum]

The IBM 386SLC has 8Kb of L1 cache and runs all Intel 486SX instructions. The 486SLC2 has 16Kb of L1 cache, as you noted. When the 486SLC2 daughtercard is on the 8556/8557, it is run from the 20MHz base clock (meaning 40MHz internally); When used on a 9556/9557 system, the base clock is 25MHz. Someday I plan to test all of the Model 56 and Model 57 systems as a comparison...

[@IBM_Museum]

There's the link from the 'Ardent-Tool' as well...

[@Epictronics1]

Thanks David. Do you know if all SLC2s are good for 50MHz? Or even faster?

[@IBM_Museum]

@@Epictronics1: The 486SLC2 daughtercards should be able to do 50MHz (although the 486SLC3 being able to do 75MHz is more evident) - I'll need to do a summary comment.

[@Davide0033]

funny thing is, varta made really good acid lead batteries, i daily use one that is like 15/16yo at this point, works like a charm

[@winstonsmith478]

Beautiful IBM hardware again.

[@rrhalo]

Another epic electronics video! Great stuffs here!

[@Epictronics1]

Thanks!

[@MoonBeamie318]

This video is probably my favorite on the channel so far, solely because of the solder work. You, sir, are an artist! Was putting this machine back together as satisfying to do as it was to witness?

[@Epictronics1]

Thanks! This IBM is all over the bench again this week. I have something interesting to show you this weekend :)

[@MoonBeamie318]

@Epictronics1 Looking forward to it!

[@sharkcz3099]

Nice job and nice PS/2 :-) But I have a question, how do you clean/wash those filthy power supplies? Thinking what should I do with my filthy AT power supply.

[@Epictronics1]

Thanks. I just wash them with warm soapy water and then dry them with hot air

[@orinokonx01]

I have an IBM Model 40SX that seemingly uses the same case! I really like that machine, because it has ISA slots :D Unfortunately, the soft-power-on power supply has died, and I need to repair it. Already recapped it, but that did nothing (kinda expected that). I suspect the power good circuit is bad. Don't leave this plugged into power! Edit: Just got to the part where you remove the power supply and mention it is not standard AT. That is true, physically. Actually, the pinout I have found indicates that an early ATX PSU would be perfectly suited to being rewired for this PS/2 power delivery style. But then trying to fit an early ATX power supply into the existing PSU chassis is not easy!

[@Epictronics1]

Yeah, you're much better off repairing the PSU than replacing it. Even if it turns out to be difficult. I will make a repair attempt on my Model 70 PSU (no power good). Hopefully in one of the videos in December.

[@custm42435]

I use OPL3LPT on my microchannel machines for sound I have it on My P70 Including an external Backpack Cdrom. I also upgraded the CPU in My P70

[@IBM_Museum]

Nothing about upgrading the VRAM?... 😁

[@Epictronics1]

I'll order some ZIPs and try them out in a follow-up vid :)

[@Thelemorf]

Maby the heavy bracket thingy is to get decent center of gravity for stability reasons when used in tower position?

[@adamfrbs9259]

I had an IBM PS1, new in the 90's....until me and the neighbor overclocked it and fried it. Haha. Parents. Not. Happy. Lol Did run faster for a bit though lol.

[@Epictronics1]

Oh, you might want to check out my IBM PS/1 videos. I have overclocked my PS/1 from 10 FPS to almost 40! That slow IBM is a real DOOM killer!

[@RedShift5]

Nice work.

[@Epictronics1]

Thank you

[@wimwiddershins]

I.B.Mgineering in that thick casting.

[@GigAHerZ64]

The 386 with L1 cache is unique enough that I wouldn't upgrade it. It's the only 386 model that has any on-die cache. I have only read about it, never seen even a video before yours! This is really cool.

[@Epictronics1]

Yes, I think we got roughly half the FPS when we ran benchmarks on the IBM with a regular 386 compared to this SLC. These are both pretty cool "386"s!

[@snap_oversteer]

Intel also made special 386 for laptops called 386SL which had integrated L1 (edit: after reading Intel datasheet, it only has integrated cache controller it seems), ISA bus controller and power management among other things. Compaq LTE Lite laptops used it, for example.

[@schnitzelsamy]

Cool

[@boardernut]

Epic video, subscribed!

[@Epictronics1]

Thanks :)

[@krizator]

That's cool!

[@autingo6583]

anybody else here have the strong suspicion that bending back the awfully bent pins with a mechanical pencil might have worked? just to make clear, i love & admire epictronics! props to the man :-D

[@Epictronics1]

Unfortunately, some of the pins were missing. Otherwise, I would have tried.

[@autingo6583]

@Epictronics1 oh okay, i didn't look closely, i was actually surprised how many pins were still there :-D

[@Epictronics1]

@@autingo6583 Yeah, that socket had seen better days :)

[@Edmilho]

Muito bacana esse computador da IBM. Dá para ver como eram bem construidos e usavam materiais de primeira linha. Eram caros também, mas é o valor que se paga pela qualidade. Parabéns pelo video, sucesso ao canal. Abraços do Brasil.

[@Epictronics1]

Thanks!

[@TravellingVikings]

These are the memory module p/n for the 8557.. IBM Personal System/2 2-8MB $1695 #5211 6450605 2MB 8MB 85ns Adapter for 857x-xxx or 8580-xxx 80386 Memory Expansion Uses #5212/#5213 Option IBM Personal System/2 $695 #5212 6450603 1MB 1MB 85ns Module for 857x-x61 (P), 1MB Memory Module 8570-121 (P), 8555-xxx (P), Kit--85ns #8286, or #5211

[@Epictronics1]

Thanks. I wasn't able to find any RAM module with that number. However, I figured out why it didn't work just now :) It will be in this week's video :)

[@OzzFan1000]

What kind of SCSI cable is needed for the external SCSI interface? I have a similar IBM (8556) that I would like to add an external CD-ROM drive to but I can't seem to confirm which drives are compatible.

[@Epictronics1]

I have not looked into this yet. I have an external SCSI drive that I plan to restore an try out with some PS/2s in a future video. I'll do some reading (and probably get or build an adapter)

[@Stratotank3r]

I love this rare and odd hardware! SLC and DLC Chips for the win.

[@elTurBoss]

The play station 2 has the same kind of rotating logo

[@tech34756]

I wonder if the bracket is either for support/stability or to make some pointy haired boss think they were getting value for money?

[@notneb82]

Did you remember to rotate the badge back for desktop mode?

[@Epictronics1]

No, I need to go back and fix it :)

[@kpanic23]

IBM PS/2 machines are extremely picky about their RAM modules. While most non-IBM machines simply try to enumerate the size of the RAM sticks by themselves, PS/2s rely on the presence detect bits. There should be one to four SMD zero-ohm resistors on the side of the module which are setting those bits. Your module, since it is not an IBM module, probably has all of those shorted to ground, so it gets detected as a 4MB 80ns module. Either remove all but the bit 2 resistor, or you might try to use some small bits of Kapton tape to insulate pins 67, 68 and 70. That should make the PS/2 correctly detect it as an 8MB 70ns module. There's a list of all the combinations on ardent-tool: memory/Reference.h tm l

[@Epictronics1]

Thanks. I need to spend some time figuring out all the different IBM SIMMs. I'm hoping we will eventually be able to make custom PCBs for at least some of them

[@dominikschutz6300]

IBM Station 2 😁

[@awilliams1701]

I'm surprised you didn't grab the re-work station sooner. lol

[@Epictronics1]

Gotta try every method ;)

[@awilliams1701]

@@Epictronics1 I'm watching you struggle and I'm like....at least use flux, but you should really pre-heat it.

[@awilliams1701]

I was also thinking you need a sweeper tip for your iron. It's nice and wide you'd be able to reflow the whole socket in 10 seconds or less. lol

[@Epictronics1]

@@awilliams1701 What tip would that be?

[@awilliams1701]

@@Epictronics1 I've seen them called sweeper tips. I've also seen spade tip and scraper tip.

[@maxtornogood]

You're too brave putting a *VARTA* branded battery in there! 😨

[@Epictronics1]

Maybe, I should replace it 😅

[@drewnewby]

We must never forget the horrors they have wrought on retro PCs. I curse towards the sky, Vartaaa!

[@kunka592]

Lithium batteries should be fine unless you're throwing them in a fire. It's mostly the NiCd batteries that leak and destroy old boards.

[@ruben_balea]

That battery pack says *...since 1887* not "...since 1987" 🤦‍♂

[@RetroShare2]

You could just solder some pins from a defective cpu. no need to remove it.

[@Epictronics1]

I don't think I have any scrap CPUs. I have however repaired a 486 ones with a broken of pin by soldering it to the CPU. It totally worked

[@j.tann1970]

Friendly advice for your English skills: Feet is already the plural word for foot so you should not add s to it to make it plural.

[@Epictronics1]

Thanks for the feedback :)

[@2xtreem4u]

🐮🐮🐮🐮🐮🐮🐮

[@MKRENB]

Why are you so obsessed with the sometimes unnecessary deep cleaning of hardware? This didn’t look like smokers pc.

[@w9gb]

Some e-waste facilities had flooding or have rodents/rats. I use Lysol disinfection wipes from unknown sources (you’d be surprised what ends up on those wipes).

[@Epictronics1]

Clean computers are more enjoyable