IBM PS/2 Model 50 (8550) September, 2018


I was at Best Buy, for whatever reason, and I was looking at the e-waste cart by the Geek Squad/Customer Service desk. It's fun to see what people are getting rid of, even though I can't take any of them.

I then noticed that someone was showing an old-looking computer to the Geek Squad and asking if they could determine if the machine worked. I was curious and walked over to see what was going on. The Geek Squad had the machine powered on and conneted to a monitor, showing an error code, but it did seem to work.

I started talking to the guy and he said he knew someone who had a lot of these, and wanted to know if they worked, how much he could sell them for and what else he could do with them.

Long story short, I bought one of these PS/2 machines... this is the story of proprietary hard drive connectors and the Micro Channel Architecture in general.

I've never used a PS/2 system before, nor an MCA system. So, I'm super curious to use this machine and see what it can do. First thing I need to do is figure out how to hook it up to a monitor. I saw the machine running before buying it, so I know the PSU is ok, but I noticed that the VGA port has a blanked-out pin. How do I connect this to a monitor?

I reached out to a tech YouTuber for advice and found out that the missing pin (pin 9) isn't used, even in modern monitors. Apparently, you canjust use a normal VGA cable, with that pin ripped out and it'll just work.

Using a VGA "gender changer," which was confusing because it was male on one side and female on the other, I removed pin 9 and connected the adapter to the machine.

I probably should've opened the machine up before powering it on, but seeing it powered up before made me believe that the PSU and capacitors are probably fine. So I connected the VGA adapter, power cable and a random PS/2 keyboard I happened to have lying around. I know that the PS/2 port was named for its use in these machines, but it's still interesting to me that a "modern" PS/2 keyboard is compatible with a machine this old.

Powering the machine on, gave me a memory count of 1024KB! As well as a few error codes - 162 and 163. Looking up these error codes reveals that the CMOS battery is dead.

I was able to source a new CMOS battery online and easily replace that. That fixed the 162/163 errors, but there were still many other errors that need to be fixed.

The floppy drive didn't want to load disks. I'd put a disk in and it felt like it was getting stuck on something, and I had to just take it back out again.

So, while I can't get it to boot into anything (since I need the floppy drive working, so I can run the setup program and configure the drives), might as well take this thing apart and see what's inside.


I got a new floppy drive. I guess I could've tried to fix the one I had, but it was just easier to get another one. I found a 50Z's floppy drive on eBay and figured that would be he same. Why would it be different?

To my surprise, it was different! The drive sled it was on was a different shape; it was angled up slightly as the 50Z has a different front panel. I tried to swap the drive sleds, but the screws didn't 100% line up.

This drive can't be completly different from the one that should be in this system, there's gotta be a way to use this. Ignoring the drive sled, I unscrewed the top of the drive and noticed the connector was able to be unscrewed from the frame.

So, I took the connector board and plugged into the system. That fit in the slot, so let's power it up and see what happens.

Interestingly, the system accepted the drive! It worked! That's one more issue fixed, now I have a floppy drive. I need to find a way to mount it correctly, but it reads floppys just fine.

I was able to boot up into the reference disk and set up the system. There is no BIOS menu, you set up the settings in the CMOS using the "reference disk." I had to download the ADF file for the 3Com ethernet adapter and copy it to the disk, but then all the hardware in the system was recognized.

Now to see what, if anything is on the hard drive. I should be able to boot into an MS-DOS (or possibly IBM PC-DOS) disk and run fdisk to see what we get.

Other than using a "weird" architecture, this system is basically a "normal" 286. In terms of software, it should be "IBM Compatible," but I imagine there may be things that won't run on here.

Some software that expects a PCI BIOS won't work, as there is no "PCI" on this system. I tried running HWInfo (for DOS), but it just sat there and didn't load.

Now that I am in DOS, let's see if we can access the hard drive. Wonder if there is anything on it.

Trying to access the C: drive gave a "File not found" error. Maybe I need to partition the disk. Let's see what fdisk has to say.

It looks like there is actually one partition on the drive, that's good. I guess it just needs to be formatted, that's no problem. let's run format C:...

This is where my problems with this machine start. The format failed. I wasn't too surprised. These old drives may have bad sectors.

I could try to low-level format the drive. That's a function of the reference disk, and maybe that'll "fix" the bad sectors.

To access the low-level format, you boot up the reference disk then press Ctrl+A, to get to a secret "Advanced" menu. From here, you can find an option to low-level format the drive.

Starting the process, the system said it was "preparing" the disk. As it was running, the "bad sector" count just kept increasing. Eventually, the format gave up and said the drive was too damaged to be used.