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Problem with sticking keys in DOS games with Socket 370 system

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First post, by Lynxman

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I have a Socket 370 system with this motherboard: https://theretroweb.com/motherboards/s/aopen-ax34-pro
It has a Pentium 3 733 now and GeForce 4 MX440 and I'm running the newest BIOS.

The weird behaviour is that keyboard keys will sometimes stick when I play DOS games after they have been held down. It will unstick once I press it again (I think that's what unsticks it). It doesn't happen when playing games through Windows 98SE. I tried changing "Gate A20" to "Fast" in the BIOS and it actually helped significantly but the problem didn't go away. I assume it's got something to do with to the motherboard's keyboard controller. I have tried two PS/2 keyboards and one USB keyboard and it's the same on all. Also tried different video cards, both AGP and PCI.

Has anyone else had a problem like this? It makes games extremely annoying at best and almost unplayable at worst. I saw Phil's Computer Lab mention similar behaviour about one of this P3 systems in a video a while back. I hoped to make this my super DOS computer but if I can't get rid of this problem I might as well just install XP on it.

Reply 1 of 10, by RetroPCCupboard

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Possibly a dumb question, but is the keyboard directly connected to the PC or is there a KVM between? I have a problem currently with a KVM causing stuck keys.

Reply 2 of 10, by Lynxman

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No nothing in between.

Reply 3 of 10, by rasz_pl

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Lynxman wrote on 2024-12-21, 20:58:

I tried changing "Gate A20" to "Fast" in the BIOS and it actually helped significantly but the problem didn't go away.

The only way this could help is if your DOS was loading something into HMA.

Lynxman wrote on 2024-12-21, 20:58:

I assume it's got something to do with to the motherboard's keyboard controller. I have tried two PS/2 keyboards and one USB keyboard and it's the same on all.

That means it has nothing to do with keyboard controller and everything to do with BIOS, or rather broken bios implementation. Maybe Bios Legacy support (USB keyboards) is permanently turned on - this makes every keypress switch CPU into SMM mode and emulate keyboard in software.

https://github.com/raszpl/FIC-486-GAC-2-Cache-Module for AT&T Globalyst
https://github.com/raszpl/386RC-16 memory board
https://github.com/raszpl/440BX Reference Design adapted to Kicad
https://github.com/raszpl/Zenith_ZBIOS MFM-300 Monitor

Reply 4 of 10, by Lynxman

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That might be.

Reply 5 of 10, by Lynxman

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Seems like it was the "keyb no" command to enable norwegian characters. Weird. I was sure I had tried turning it off already. Also weird because it's never caused a problem like this before on any system I've used since the 80's. I "rem"-ed it in autoexec.bat and played Descent 2 without problem now. None of the alternate keys match my keyboard but I can live with that for games. Might as well get an english keyboard.

Reply 6 of 10, by rasz_pl

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Could be dos somehow loading keyb BIOS extension into HMA = A20 needs to be switched every time you press a key, that can be slow on some configs and screw with CPU cache in others.

https://github.com/raszpl/FIC-486-GAC-2-Cache-Module for AT&T Globalyst
https://github.com/raszpl/386RC-16 memory board
https://github.com/raszpl/440BX Reference Design adapted to Kicad
https://github.com/raszpl/Zenith_ZBIOS MFM-300 Monitor

Reply 7 of 10, by myne

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Could try changing the "typematic rate"in the bios

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Reply 8 of 10, by Lynxman

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I haven't tried them but I don't think typematic rate settings will work well in games because there's always a minimum of 250 ms between the first generated stroke and the next.

I have some alternative language TSRs that I can try.

Reply 9 of 10, by Lynxman

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The same happens when I try the other modern "low memory" TSR.

I ordered an american keyboard. Don't need ÆØÅ to use this computer anyway.

Reply 10 of 10, by rasz_pl

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try to disable DOS HMA (high memory area)

DEVICE=[drive:][path]HIMEM.SYS [/A20CONTROL:ON|OFF] [/CPUCLOCK:ON|OFF]
[/EISA] [/HMAMIN=m] [/INT15=xxxx] [/NUMHANDLES=n] [/MACHINE:xxxx]
[/SHADOWRAM:ON|OFF] [/TESTMEM:ON|OFF] [/VERBOSE]

/HMAMIN=m
Specifies how many kilobytes of memory an application must require for
HIMEM to give that application use of the HMA. Only one application can
use the HMA at a time; HIMEM allocates the HMA to the first application
that meets the memory-use requirements set by this option. You can
specify a value from 0 to 63.

maybe "/HMAMIN=63" will be enough to dissuade your language handling driver from loading into HMA

https://github.com/raszpl/FIC-486-GAC-2-Cache-Module for AT&T Globalyst
https://github.com/raszpl/386RC-16 memory board
https://github.com/raszpl/440BX Reference Design adapted to Kicad
https://github.com/raszpl/Zenith_ZBIOS MFM-300 Monitor

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