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Rediscovering an old IBM PS/2 Model 50
By Thom Holwerda on 2017-02-15 21:51:11

Today, after sitting in storage for over 20 years, my brother and I dusted off his old IBM PS/2 Model 50 (8550-021), with the goal of cleaning it up and making sure it still works. It was still working when he stored it, so it should still be okay today (barring any unavoidable degradation caused by the slow march of time). As far as he remembers, it's got DOS installed on its 20MB hard drive (and a bunch of games).

I've taken it apart completely so that I can set to cleaning it thoroughly tomorrow. Everything seems to be in relatively pristine condition (save for the case, which is battered in a grungy, industrial kind of way). A visual inspection didn't reveal anything blown or out of the ordinary on the motherboard or HDD/FDD riser cards, and from what I can tell without opening it up, the PSU seems to not feature any blown caps either.

Originally, I was planning on just getting some cheap PS/2 keyboard and mouse somewhere (turns out none of us owns any of those any more), but the more I was awestruck by the industrial beauty and elegance of the PS/2 and its modular internals, I felt overcome by a strong urge to do this machine justice - assuming it still works, I'm buying the original PS/2 mouse and IBM Model M keyboard. It's the least I can do.

I've also been looking at other ways to expand and upgrade the device (which I'll do only after having confirmed it still works, of course). I've found an AST Advantage/2 RAM expansion/SCSI controller 16-bit MCA card (with 4MB of RAM installed) in an online store, which would be a neat way to add some additional memory to the machine. It's a multifunction MCA card that adds 8 RAM slots and a SCSI interface to the PS/2. I'm not entirely sure how these additional RAM slots work (i.e., does any RAM get added to extended memory?), but for its relatively low price, it seems like an interesting exotic piece of hardware to own either way.

There are other, far more substantial upgrades and peripherals I'd like to add to it, such as the IBM 486SLC2-50/25 processor upgrade kit (incredibly rare and prohibitively expensive if you do find one) or a math co-processor (haven't been able to find one, and would be rather useless for running a few DOS games anyway). Additionally, there are rare things like an MCA Sound Blaster or SGI IrisVision (more information) that'd be awesome to have, but I doubt I'll ever find them. I'd also love to get my hands on a matching IBM PS/2-era monitor, but I highly doubt I'll be able to find one that is in relatively good condition, close enough so I wouldn't have to ship it (dangerous), and not incredibly expensive.

This (admittedly modest) project has me quite excited, and I can't wait to see if it still works. This is not some disposable, faceless early 2000s Compaq or whatever - this is an iconic and truly classic machine that deserves care, attention, and continued periodic maintenance, even if it'll only serve as decoration. You don't just throw out or dump an IBM PS/2, and I possess the skills and passion to keep it in working order, so why not do so?

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Read Comments: 1-10 -- 11-20 -- 21-30 -- 31-35
Thrown away
By Alfman on 2017-02-15 22:18:16
I had a very similar if not identical system to that 486 with the co-processor. We threw away most of that stuff when I went to college. Still have an old IBM PS/2 laptop like this one that probably will get purged as well.


I bet we all have tons of crap just sitting somewhere collecting dust over the decades.
Permalink - Score: 3
Agreed on the power switch
By timl on 2017-02-15 22:18:47
I once owned a PS/2 model 70, I believe, and I loved the lever and the fact it was on the *front* instead of on the side near the back. That said, I'm pretty chuffed with modern push buttons and (related) suspend capabilities.

Also, your brother (presumably) had a good taste in music ;)

Edited 2017-02-15 22:24 UTC
Permalink - Score: 1
RE: Agreed on the power switch
By joekiser on 2017-02-15 23:39:50
I had about half a dozen Model 30's, and a Model 50 something that I'm pretty sure had a 486 with a 50 MHz processor.

They were being thrown out by the local community college, so I took them home. Keyboards, monitors, PS/2 mice and all. I was probably 11-12 years old and it took several trips.

They mostly all worked, some would boot to DOS and some would go to some kind of BASIC. There was a mismatch of 720k and 1.44MB floppy drives, and some had a 5MB hard disk drive in them. Some monitors were monochrome if I recall correctly. I could get Windows 3.1, not the WFW version, to install and work reasonably well on the higher end machines. Wolf3d would run; Doom would not. Prince of Persia had a satisfying feel on the keyboard.

I was a poor latchkey kid and one of the few times I got in trouble, it was for trading my original NES at a yard sale for DOS 6.22 to install on these machines. Probably not a good deal a the time, but I learned a lot more from those PS/2's than I would have from the NES.

I found that the 30 pin SIMMs from the 486 fit and worked perfectly in the family Packard Bell, so we ended up with 12MB of RAM in that machine.

When I graduated college, I vowed to clean out the bedroom at my parents house and sell all of these computers. I got an offer for $300 for the whole setup from Craigslist, but ultimately couldn't part with them. So that's where they are sitting ten years later. Minus one Model M PS/2 keyboard. I brought that with me to South America and am typing on it now.
Permalink - Score: 2
RE: Agreed on the power switch
By WorknMan on 2017-02-16 00:20:07
> I once owned a PS/2 model 70, I believe, and I loved the lever and the fact it was on the *front* instead of on the side near the back. That said, I'm pretty chuffed with modern push buttons and (related) suspend capabilities.

Man, I would love those old levers back. When I'm turning off the PC using the hardware switch, 99% of the time it's because the software is locked up. Hence, when I hit the off switch, I want the f--king thing to turn off IMMEDIATELY. At least give me the option in the bios for a double press or something :P

Edited 2017-02-16 00:20 UTC
Permalink - Score: 2
RE: Thrown away
By malxau on 2017-02-16 01:02:09
I'm pretty sure my family still has two of those 486DLC boards; I didn't know they were valuable. At the time it was just a cheap way to upgrade a 386 system without throwing it in the trash, although the upgrade itself performed pretty well - I was happy running Windows 95 on those machines whereas my friends weren't happy doing that on the native 486DX2s of the day.

It ended up being obsoleted once I was trying to do much more computationally intensive work, like javac (groan.)
Permalink - Score: 2
beautiful machine congrats! :D
By sergio on 2017-02-16 06:06:20
It had a VGA monitor back in 1987!! A-ma-zing!!

My first 286 back in '89 had Hercules monitor cause a VGA monitor cost more than the entire computer haha

I even dreamed about VGA monitors back in the day I really really wanted one (to play videogames obviously)... my dad finally bought me one a couple of years later around '91. And even at those times it was damn expensive. (got the VGA monitor with a pirated copy of "Another World" hehe)

Ah, the good old times...

Edited 2017-02-16 06:09 UTC
Permalink - Score: 2
IBM PS2 55SX owner
By gilboa on 2017-02-16 07:18:50
I really miss that machine.
Even though it cost me - in relative terms - more than my current dual Xeon workstations, it was amazing machine.
2MB RAM, VGA, 20MB drive. It ran circles around the old 8Mhz XT machine it replaced.

Sadly enough I was stupid enough to sell it and replace it by a no-name 486/50 machine :(

- Gilboa

Edited 2017-02-16 07:21 UTC
Permalink - Score: 2
By hackus on 2017-02-16 11:09:13
I myself just finished rebuilding the video and analog power board assemblies of an original VT102 terminal which I keep as my kernel workstation for my HADOOP cluster.

Old Equipment is fun! :-) However, for me the VT100 series is not only ICONIC, it was how I learned C by writing a terminal display driver for my BBS software on my Atari ST.

It greatly affected my development in computing.

Load LINUX on it. :-)
Permalink - Score: 2
Why didn't you just plug it in
By joshv on 2017-02-16 12:52:48
All this work before you even try to see if it works? Plug it in, if it releases the magic smoke, move on.
Permalink - Score: 2
By bhtooefr on 2017-02-16 12:58:37
Looks like the early MCA PS/2s actually scanned through RAM, and remapped failed RAM out of the memory map. On a 386 (the Model 80), this was simply done by programming the 386's MMU (although now I'm wondering just how involved the PS/2 BIOS is - does this mean that booting DOS on a 386 PS/2 started in V86 mode?)

On a 286 (Models 50/60), however, this was done externally to the CPU, using "translation RAM" to store a mapping between the addresses the CPU sees, and physical addresses. So, it could easily map out bad RAM... but the TRAM could be mapped however you wanted, really, and QEMM 50/60 took full advantage of this to give EMS 4.0 on a PS/2 Model 50/60.

Here's the problem... apparently the AST Advantage/2 didn't have any TRAM, so the whole card is mapped into the CPU's address space directly. That means it's XMS - fine for OS/2, *nix, and Windows 3.x, but you're not getting any EMS, so not as fine for some DOS stuff or Windows 2.x.

Edited 2017-02-16 12:58 UTC
Permalink - Score: 4

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