That or find an AOX MicroMaster 386 or the later Kingston MCMaster 386/486. Both are CPU upgrade cards for the Model 50/60 and have additional RAM slots. I have a AOX 386 card here with a missing 386 and broken SIMM retention tabs. Stupid plastic garbage.

I hadn’t noticed how bad the conventional memory situation is in OS/2 1.x before – it didn’t include MEM.EXE and was such a bad runtime for DOS programs it never mattered. Looking now I think you nailed it with bimodal drivers – I hadn’t heard of this before, and while it makes sense to have a single mouse driver for DOS and OS/2, a lot of drivers look to be loaded here that shouldn’t be. I’m seeing things like PMDD for example – what is DOS supposed to do with that?

For the leaked XMS, my understanding is that HIMEM.SYS is providing mechanics to copy memory around and also providing a simple allocator to track which XMS regions are in use and provide handles to them. Unfortunately this is all before the current concept of a “process” so there’s no reliable way to clean these up on exit. I suspect you’re seeing leaks from EMM286 rather than Windows, because a) it needs to allocate XMS and b) it sounds less mainstream/thoroughly tested. I’d be curious if you use 1Mb EMS instead to see if the leak still happens (3Mb being much larger than a 286 would typically do.) Oh, and agree with Stefan that it needs to copy as opposed to remap, which would make it very slow.

For EMS on OS/2 1.x, MSD is showing the memory range needed for it is available, and the “bimodal driver” design would actually help here. It seems like it ought to be possible to do. Although rather than do that, it might be more interesting to turn OS/2 1.x into a DPMI server…

Ive been under the impression that LOADALL is much more faster, but yes there is this implied loss of speed from A20 gating, changing modes, and shuffling data around. I didn’t think the overhead would be so bad, when looking at disk speed timings when comparing a few himem.sys types (xmsmmgr vs Windows 3.1 himem.sys) and smartdrv on / off, which was so minimal.

Indeed the only way to tell is a legit EMS card, however at the moment the only MCA card market I’ve managed to crash is the SCSI market. RAM cards are still ~ £100-£250 range. Which is a shame. I should have probably jumped on an 8580 20Mhz motherboard for £130, that would have been a big bump in performance, and of course giving me access to v86 mode & 32bit software.

The way I imagine EMM286 works is by copying to and from XMS memory every time the EMS client changes the mapping. At least I cannot imagine how it would work in any other way without a V86 mode (and without support from the chipset). Yes, it needs to switch modes, but it also needs to copy memory around a lot, which likely plays a much larger role.