Thallanor wrote on 2020-08-20, 21:00:

AlessandroB wrote on 2020-08-17, 19:44:

Thanks for your experience, what stop me now is the fact that mine board come with only 64kb of ram.

Much like waterbeesje said, I think you'll be able to find solutions. I know that since I bought my AST SixPakPlus, I've seen other 8-bit memory boards that claim to host up to a full 640K of RAM. You might also be able to populate your motherboard to at least 256K, using more or less off the shelf chips, and then use something like the SixPakPlus (or a myriad of other boards) that might not do 640K, but do 384K, and combined with a maxed-out motherboard, bring you up to 640K. I am absolutely exhausted right now, but seem to recall that you _might_ need a newer BIOS to support some things (in fact, I'm trying to remember if the XT-IDE was one of those things requiring the latest...) but I've seen people offering to prepare ROM chips for others on request. You definitely have options. It's a fun little (big) computer. 😀

Hello! Despite popular belief, 640KB have never been the maximum, though.
That's as correct as the old claim that QDOS was nothing but a CP/M clone (it's not that simple). 😀
In the 1980s, 704K or 736KB of memory had been perfectly normal for XT class computers. It's a period correct configuration, in fact.
Back then, professional users were desperate for memory and 640KB were not enough.
Just lets remember Lotus 1-2-3 which ran out of memory quickly and essentially gave birth to Expanded Memory (EMS).
Or the disaster with DOS 4 that took up to much RAM.
From the IBM PC, over the BBC Master 512 to the x86 emulators for Atari ST (PC-Ditto, AT-Once, AT-Speed etc) and Amiga (PCTask), machines were capable of 704KB.
In fact, except for the IBM PC, these menioned before shipped with 704KB minimum.
Even OS/2 had a special "CGA" mode option for its DOS VMs, too, providing 736KB of DOS RAM..
Here are some links with sources and pictures:
a) 80x86/Vxx PC emulators with x87, EMS, UMBs and no artificial 640KiB limit ?
b) http://annex.retroarchive.org/cdrom/nightowl- … 011A/704RAM.ZIP
c) http://annex.retroarchive.org/cdrom/nightowl- … 011A/RAMSET.ZIP
d) https://youtu.be/8nMB8XvwUJo
e) Re: most compact 8088/8086 board you've seen?

Last, but not least:
"I have found out that IBM PC 5150 continues BIOS memory test to 704 kilobytes with undocumented SW2 DIP switch settings ON ON OFF ON OFF and DOS automatically uses all of that as conventional memory. This is an alternative way to utilize 64 kilobytes of RAM at segment A0000."
Source: http://www.vcfed.org/forum/showthread.php?317 … 4000#post444000

That being said, it's not my fault that, -according to these facts-, reality was different than what most people of today believe.
Personally, I have no issues with either version. Period-correctnes is nothing that worries me at all. 😀

At worst case, I'm just confused by nowadays emulator writers (PCem/86Box etc) who don't allow a 704KB configuration at all.
Their predecessors on the Atari/Amiga platforms had no issues with this 30 years ago.
They programmed their emulators in a practial way instead of preserving the 640KB barrier as if it was some sort of religious relic. 😉

Edit: I would like to apologize, I didn't mean to sound unfriendly. What I wrote was solely about the matter itself, I didn't mean to criticise any of you in any way.
What you said/wrote was not incorrect, after all. Boards like the SixPakPlus allowed for a max. expansion of a 640KB.

Incredible, your competence on the subject is boundless.

In reality I did not plan to go beyond 640kb because I did not think that my use of this computer required it, my intent is not to find out how much ram my IBM can use, but to discover the possibilities of this computer (I have already the motherboard version with the maximum amount of supported ram and the latest release of the bios) and for this I got an ATI VGA / EGA Wonder 16, I will get an IDE-XT, I'm not sure about a sound card yet but I think not, but what I miss is to get to a quantity of ram (now I have only 64kb as already written) to be able to use the computer to the maximum of possibilities. I was curious to see if I could run some EGA or even VGA games.

You're welcome. 🙂 For EGA/VGA systems, 640KB is the maximum.
But you can still use an RAM card, so you can use UMBs (to load drivers high. Games like Commander Keen 4 may also use it) .
That 1MB Lo-tech card, for example, is made for the IBM PC, and can also work in slot #8, I think.
To make UMBs visible to DOS, a little DOS program is needed.
Alternatively, an EMS card is also nice to have.
Programs like DESQView, PC/GEOS, Win3, etc can benefit from extra memory.
Anyway, these are just ideas. 😅

"You're welcome. 🙂 For EGA/VGA systems, 640KB is the maximum."

You have hit the target, I prefer to discuss with you the ways to get a machine as close as possible to its time and at the same time allow me to run software that amazes me on it. So I can say: "I didn't think I could play this game on an IBM pC 5150!" I got it?

I think the base system already has an advantage with the latest version of motherboard, I think the graphics card is excellent and the compact flash drive is by far the best compromise. Now I need to find the chips to expand the mainboard to its maximum and find a ram card to reach the fateful 640kb. Can you help me with these two searches?

I got 16 "Sharp LH21256-12" branded ram chips, can I use them to expand my IBM 5150 mainboard? tnks