Increase the 3000 byte buffer in Nvidia driver

gpinzone

There is a community of us who use nvidia cards inconjunction with MAME and multisync arcade monitors. In the quest of getting as close as possible to the real arcade games of old(pacman, donkey kong, etc..) there is a program out there called SOFT 15KHZ. What it does it allow Nvidia and ATI cards to run and at very low resolutions.
International Overview - arcadeinfo.de Arcade Community
o 15kHz
 240 x 240 @ 60Hz
 256 x 240 @ 60Hz
 256 x 256 @ 60Hz
 256 x 264 @ 60Hz
 304 x 240 @ 60Hz
 321 x 240 @ 60Hz *
 321 x 256 @ 60Hz *
 336 x 240 @ 60Hz
 352 x 256 @ 60Hz
 352 x 264 @ 60Hz
 352 x 288 @ 50Hz **
 368 x 240 @ 60Hz
 384 x 288 @ 50Hz **
 392 x 240 @ 60Hz
 401 x 256 @ 53Hz * **
 448 x 240 @ 60Hz
 512 x 240 @ 60Hz
 512 x 288 @ 50Hz **
 632 x 264 @ 56Hz **
 640 x 240 @ 60Hz
 640 x 288 @ 50Hz **
 640 x 240 @ 60Hz
 512 x 448 @ 60Hz Interlace
 512 x 512 @ 60Hz Interlace
 640 x 480 @ 60Hz Interlace
 720 x 480 @ 60Hz Interlace
 800 x 600 @ 50Hz Interlace **
 1024 x 768 @ 50Hz Interlace **
* "Fake"-Resolution to avoid DirectX-Problems.
** Says 60Hz in Windows.
o 25kHz
 448 x 384 @ 60Hz
 512 x 384 @ 60Hz
o 31kHz
 512 x 448 @ 60Hz
 512 x 512 @ 60Hz
 640 x 480 @ 60Hz
 720 x 480 @ 60Hz
 800 x 600 @ 50Hz **
 1024 x 768 @ 50Hz **
This allows us to display arcade games very close to their original resolution. Soft 15khz accomplishes this by adding those resolutions to the registry. However these resolutions that you see above work for about 95% of games. Unfortanuatly a lot of the classics like pacman run at say 304x240@58z. This casues games sound and graphics to stutter because of the 2hz difference from the original game. This can easily be fixed adding an addition modeline to reflect the proper resolution and refresh rate through Soft 15KHZ, however there is a limitation with Forceware drivers
Theres a limit of 32 modelines with Nvidia drivers
A "bug" in the ForceWare.
They read/write from/to the CUST_MODE registry key with a 3000 byte buffer, while one mode is 92 bytes.
32 Modes * 92 Byte = 2944 Bytes = fine.
33 Modes * 92 Byte = 3036 Bytes = buffer overrun.
If you add more modes via the default NVidia controls you'll end up with garbage in the registry the first way.
If you add more modes via Soft-15kHz the data in the registry is fine.
However, on bootup, the driver reads only those 3000 bytes, which cuts off the 33rd mode and anything behind it, causing the whole CUST_MODE string getting detected as "faulty" and droped, hence the card generates the modes itself IN 31kHz.
This was taken from this thread Soft-15KHz - slim new tool for 15KHz on normal vga cards
Can the 3000 byte buffer be increased in the driver? If so there would be a lot of grateful people in the arcade cab mame community.


Is this possible. Any help would be appriciated.

LukeK

did you try asking catalystcatcher? some AMD staff members on the forums here. sounds a rather technical question i doubt the public would even know what you are talking about.

gpinzone

Its not a ATI issue its an nvidia one.