You don’t need it they said!
Well it’s been no secret, but OS/2 6.123 on my PS/2 model 80, is insanely unstable running simple MS-DOS based games (large EXE’s)
And almost always I’d get this fun error:

Followed by a crash trying to execute code at the top of the memory MAP (ABIOS?)

Then ending the program will just crash OS/2. Very annoying!
My goto test of v86 mode environments is an old game that I enjoyed as a kid, 1988’s BattleTech the Crescent Hawks inception.

It’s a great game, that runs on many 8-bit/16-bit systems of the era, and is surprisingly a very well behaved MS-DOS game. I mean if Windows/386 VGA machines can run it in a window using the CGA version, surely a super early OS/2 2.0 beta (6.123) can run it, right? However I found 6.123 to be incredibly unstable, and sadly not up to the task.
I tried to launch BattleTech over and over and had zero success. I couldn’t figure out why it was struggling on my model 80 board, where it runs just great on 86Box. What is going on?
One thing I had stumbled upon was that if I launched an ancient Infocom game in a DOS box, and then launched BattleTech it had a much higher chance of running. But this did not always equate to it working. How is launching an old COM file from the early 80’s excise the ‘devil’ of some 1988 EXE from running?

I wasn’t sure but I had this weird suspicion that it was that my system was lacking a math coprocessor. When I had the model 60 286 board in the PS/2 case I did spring for an 80287, and one thing I found is that OS/2 1.0 & 1.21 ran great. As a matter of fact I think it ran better than when I used to have a 386sx-16 and then later a 486SX-20. Now it’s been closer to 30 years, so I could have an absolutely false memory of all this, but I wasn’t sure I was onto something. So while shopping around a subscriber offered me a math coprocessor as they seem to be insanely expensive in the UK. I have no idea why the 80287 was so cheap, and no idea how to make any kind of adapter, but pJok was able to score one for super cheap in his homeland and send it to the barren wastelands of Scotland. As I was wrapping up the SSD G5 fun, the coprocessor arrived, and it was time to install it!

The PS/2 8580 motherboard is really oddly designed with chip orientation going in every which other direction, and the 80387 socket isn’t keyed by pin, so it’s vital to see the notches on the silkscreen. Otherwise I just used compressed air to blow out the socket, and run the reference disk to add the processor.

The processor was instantly picked up, although I had the crashing issue with the BocaRAM/2 memory card again, which meant I had to remove the RAM card, re-configure with the math coprocessor, then add the RAM card, reconfigure, then run the util to patch the CMOS so it’d boot up. I really dislike this RAM card, but 32bit cards cost far more than this entire endeavor cost so I’m pretty much stuck with it.
Now let’s compare the Landmark scores between the 286/287 and the 386/ITT387

And now the 386:

The ITT pro