>MEMSIM32

so you tried to download more ram 😀

I'm afraid there isn't anything you can do.

When you put DOS=UMB in CONFIG.SYS, after each DEVICE= or DEVICEHIGH= statement, it causes DOS to check whether there is an XMS driver installed, and if there is, it grabs all the UMBs that the XMS provider offers for its own use by later DEVICEHIGH= or LOADHIGH (LH) statements. Since you don't have a UMB provider in any normal XT class machine, DOS=UMB is a no-op.

The UMB provider everyone is familiar with is EMM386.EXE. In fact, during "period correct" times, I personally (and I suspect others) didn't realize that there were other UMB providers than such EMM programs, and that it's even possible to have UMBs on 8088 and 286 machines. So I don't think you will find any books from back then useful as they will gloss over this. The only requirement for a UMB provider is that it provide an XMS control function, and that it provide XMS function 10h (request upper memory block).

UMBs in turn represent RAM with a segment address between A000 and FFFF. On a 386 it is easy to remap memory there without chipset support using 386/V86 mode paging. I don't know of any "period correct" 286 or 8088 implementations. In theory, any chipset that supports EMS or EMS card could theoretically be asked to put a 64K EMS page frame at D000 (for example), fill it with four 16K pages, then simply "forget" about EMS support, locking those pages in place, and hand it over to DOS as UMBs instead. Even better is a specially designed memory card like the LoTech 1MB that, rather than bothering with EMS, simply allows you to fill up C800-F000 with 160K of RAM, then you use a UMB provider like USE!UMBS that is a "no op" in terms of messing with chipsets or hardware, and is simply there to inform DOS that there are available UMBs in that space. A normal, period correct XT or AT including your Epson does not have any UMBs there. In contrast, there are some "modern" XT clones like the Homebrew8088 that intentionally put some extra 32K of memory at an address like F000, and that can be used as UMBs in DOS 5+ with an appropriate driver added to config.sys.

The driver you are using sounds like a "LIMulator" which is unlikely to help you. It costs you significant conventional memory and doesn't serve any purpose other than satisfying any programs that demand EMS, yet where the performance hit caused by swapping to disk and back doesn't hurt much. In other words, maybe something like Lotus 1-2-3.

+1

There used to be RAM cards that also could be used to provide free UMBs.

There's a photography in my older thread over here: Re: 80x86/Vxx PC emulators with x87, EMS, UMBs and no artificial 640KiB limit ?

It shows the homebrew version published in an old issue of c't magazine.

A modern version is the Lotech 1 MB card, which had been cloned a few times.

For EMS, there is a 2 MB card by same company.

If free slots are running out, it's possible to piggyback ISA cards. It's a parallel bus, after all.
Or use hybrid cards with multiple devices on one card.

Edit: The good thing about EMS is, that various programs can access it.
The 64KB page frame is a sacrifice that can be worth it, depending on the use case.

Most applications in MS-DOS 6.2x can use EMS, for example.
GUIs and graphics programs may also make use of it. So yeah, it's a personal decision, maybe.

NHVintage wrote on 2023-11-04, 21:35:

I seem to recall there is a program that could leverage video memory - I have a Trident TVG8900 EVGA card with the maximum amount of memory on it, I believe thats 1MB, maybe that would help?

Thanks!

Actually, you might get somewhere with this. I don't recall exactly but if you only use mono mode or only use color, there might be some spare VRAM at A000 or B000 you could repurpose as UMBs. USE!UMBS or another similar utility could be of help there.

+1

QRAM comes with such an utility, I believe.
VidRAM or something along these lines.

There's also an utility for Hercules Monochrome Graphics card. Unfortunately, I never got it to work.
Probably, because I was using HGC clones and not the real card.

Great suggestions. I tried adding VIDRAM.COM to the config.sys, with and without the EGA switch, and it just caused the PC to hang at startup. I took out all the memory 'enhancers' - QRAM, DOSMAX, and MEMSIM, and left in DOS=UMB, and it says I have 589k for programs. Which is the most I've seen. I'm not sure how MEMSIM32 works but the MEM command, at least, doesn't pick it up, so I can't tell if its doing anything. Bear in mind I have to use MS-DOS 5, as that's the last version that comes on 720k disks and that's all the Epson can handle. At least until I can figure out how to install DOS 6.2 from either the USB drive (I have one of those ISA-USB cards, which makes it a LOT easier getting files onto the C drive, which is and SD card) or from C itself.

Someone mentioned 'piggybacking' ISA cards - how? I've looked for ISA adapters and such and haven't seen anything that looks like it would do that.

Upgrading DOS can't help here.
The higher DOS version, the more RAM it occupies.
Later DOS versions allow to compensate for that by loading certain stuff above the 640K mark, but it requires 286+, even better 386+.

For an XT with HDD <= 32 MB, the perfect DOS version is 3.30.
For larger HDDs, 5.0 may be necessary, though 3.31 may also be worth trying.

I have a ton of "HDD" (SD card space) and 5.0 is installed already, so I might as well stick with what I have. But I have on the way a WE AM20 DC 180100C Memory expansion card that has a floppy interface on it, that has a daughterboard interface that I want to experiment with, so stay tuned and I'll report back results on it. It helps I'm not looking for a full 1MB, just a wee bit more, and perhaps I can expand UMB enough to move drivers TSRs etc to it. It was cheap enough and if it isn't useful here it's bound to be on another project...

Unbelievably, my local recycling company posted a Tecmar XT Expansion Chassis for sale today and I snapped it right up, thus solving the problem of not having slots available. I'll pick it up in the next couple of days.

NHVintage wrote on 2023-11-08, 02:01:

Unbelievably, my local recycling company posted a Tecmar XT Expansion Chassis for sale today and I snapped it right up, thus sol […]
Show full quote

Unbelievably, my local recycling company posted a Tecmar XT Expansion Chassis for sale today and I snapped it right up, thus solving the problem of not having slots available. I'll pick it up in the next couple of days.

this is pog

well, it will be if it has both cards, but I'm actually expecting that it'll be missing the PC end and it'll be a longer term 'wait til I snag the card I need' project. But it IS the ultimate solution. Eventually.

Congrats! 😃🎉

That's the positive side about slow paced 8-Bit systems.
The cable lenght can be longer at lower MC/s.

Unfortunately the PC-side card for the expansion chassis is missing, as I expected. The expansion chassis card is there as are the cables. I paid a good price so I will just wait until either I find that Tecmar card, which may be awhile, or perhaps try the solution I saw elsewhere that lets you attach an ISA backplane to the rest of your PC. Though the idea of finding an 8-bit industrial SBC and putting that in the expansion chassis, thus making it a standalone, is intriguing too, perhaps.😁

But I did get 2 early logitech serial mice and a mouse systems 3-button mouse (only partly working at the moment) along with a chrome metal PS/2 mouse I could genuinely hurt someone with if I used it like a bolo, for $20. 🤣.

The IBM expansion chassis transmitter card has been reverse engineered and cloned. No idea if the tecmar one is a 100% copy of it or even compatible though.

I haven't found any clones except 1 or 2 in poland for as much as an original if not more. The tecmar ones are different but do the same job - I could use a pair of either Tecmar or 5161 cards. but I can't use one of each. Do you know where I might find the clones?

https://github.com/schlae/ibm-extender

Ah, a project. That's beyond my skills I'm afraid, at least for now. I was hoping somoene was actually selling them somewhere. Thanks, though! I actually did more investigating and I found a few 16-bit AT cards for extending to another chassis by Acces I/O and Contec, among others, but I'm not at all sure that they'd work in an 8-bit slot like some 16-bit video and sound cards do. Plus, those connect with a 96-position amphenol connector (not a D-sub like the 8-bit IBM extender set), and I searched all over and they're at least $200: https://www.ebay.com/itm/404516495009 Also the original IBM extender cards run around $500 a set now, without a cable.

I've just set a saved search on ebay and will see what happens. I can wait, it's just a hobby thing.