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Old 08-29-10, 04:13 PM   #1
Malichite
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Default GeForce GTX 285 and nvFlash will not change device ID?

Recently I picked up a cheap GTX260-216core (55nm) and naively thought I could simply run SLI with my GTX285 (55nm) given they are both gt200b based albeit with fewer shaders and lower freq. I figured I would just have to SLI with the slowest card and the least common shaders (i.e. GTX260's 216 versus GTX285's 240), but it appears that nVidia's SLI driver simply compare DeviceIDs before allowing SLI mode. I am able to SLI my brother's GTX260 (65nm) version with my GTX260-216(55nm) version fine, but I would prefer to keep my GTX285 as the primary for solutions when SLI doesn't work so hot. Thus I am almost positive my issue for the missing SLI option on my 790i motherboard is the deviceID of the 260 (both the 55nm-216 shader and 65nm 192 versions are 05E2) and the 285 (05E3) are being detected as different. I tried to simply change the deviceID on the 285 BIOS, since I can downclock it later with software, but even though the flash says successful the deviceID is maintained. If I dump the newly flashed bios back out and read it in nibitor it has my modification. Further, if I run nvflash --version I see the new deviceID in the later EEPROM details, but the first line in the version report still has the 05E3 and likewise in Win 7 GPU-Z still sees the original deviceID of 05E3.

Am I missing a critical flag in nvflash (--index =1 -4 -5 -6 BIOS.ROM and yes to all dialogs)? I know that there is an issue with the newer cards being protected from being turned into Quadros, but I thought there wasn't an issue if you were just changing the last # of the device ID. I would appreciate any thoughts on this and I really don't want to try to flash a 260-216 complete bios over the 285 or vice versa since they have different options in the VRM section and possibly timing sections, so I would prefer to just spoof the deviceID.

Thanks,
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Old 08-30-10, 01:17 PM   #2
frenchy2k1
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Default Re: GeForce GTX 285 and nvFlash will not change device ID?

Device IDs are actually burnt into the chip, so a simple BIOD flash cannot trick it.
The only use you could have for the 260 is as a Physix card I guess...
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Old 08-30-10, 06:54 PM   #3
Malichite
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Default Re: GeForce GTX 285 and nvFlash will not change device ID?

I am not sure that is entirely true that the whole deviceID is unchangeable, but I do agree that the simple hack of dumping the ROM, changing the deviceID in nibitor, and reflashing doesn't work. I found a few cases when someone RMAd a GTX280 and instead got a GTX285 as a replacement, which disabled SLI enable due to different deviceIDs. Their final solution was to flash a GTX280 bios over the top of the GTX285 and it appears to have worked as it enabled SLI again. That is far more risky that I would attempt since there is a chance for issue with the timings and VRM section, but at least that suggest there is another place the deviceID is found in the bios if their attempt changed the deviceID from 05E3 (GTX285) to 05E1 (GTX280). I also found some info on a site trying to hack a GTX to a Quadro and they seem to suggest that the last digit of the deviceID was modifiable, but given 0x05E1 for the GeForce GTX 280 and 0x05FD for the Quadro FX 5800 nVidia protected itself from the soft strap methods to enable the professional version.
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