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Old 02-02-09, 02:24 AM   #1
xorbe
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Join Date: Jun 2005
Posts: 388
Default downclocked ROM on EVGA GTX260 SSC 55nm (-1258-)

Finally figured out that Far Cry 2 would stop crashing if I lowered the stock shader clock on my card. Lowering the core clock also removed occasional visual glitches. Memory clock seemed fine as I could inch it up without crashes (with lowered core/shader), but I lowered it also for good measure. I thought to exchange for a "regular" card, but this is supposed to be a cream of the crop chip (despite EVGAs failed qualification attempts), so I wanted to keep it and downclock it myself. Shipping isn't free anyways for exchanges. Yeah, you could do it manually with EVGA Precision or have RivaTuner change it on each boot, but that's cheesy, and I need this to work in Linux too. Here is the straight dope on getting this done.

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Burn this bootable Win98 iso to a CD.

http://www.onecomputerguy.com/software/win_boot.iso

Make a FAT partition on your HDD (may be painful to do, but if you have no floppy drive and your USB isn't working properly like mine after booting the CD...) Or, put the files on a USB stick, and check if C:/D: shows your USB stick after booting the CD. Mine showed up as C:, but running "nvflash --list" just hung no output. If you have a floppy drive, format a boot disk, and you have the easy way.

Download nvflash 5.72 and drop onto your FAT drive/floppy/USB stick.

reboot with CD.

C: (if using harddrive or USB)
nvflash --list
nvflash --save stock.rom
copy stock.rom modified.rom
dir

Remove CD and press ctrl-alt-del

Download NiBiTor v4.8 and open modified.rom file.

Change 675/1453/1151 to 626/1352/1080 (this basically cuts the "stock overclock" in half).

Save the ROM file.
Close NiBiTor, run again, load modified.rom and verify your handiwork.
Reboot and boot with CD.

C: (if using harddrive or USB)
nvflash --check
nvflash --protectoff
nvflash modified.rom
nvflash --protecton
dir

Your card may emit a beep with protectoff, the flash, and protecton (mine did).

Remove CD and press ctrl-alt-del, and pray that it worked like it did for me!


Keep a copy of your stock and modified ROMs, nvflash, and NiBiTor.

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I also note that the "3D extra" (ie, 675/1453/1151) voltage is set to 1.18v by default on this card. (EVGA 896-P3-1258-AR)
Stock clocks are 576/1242/999 for reference. I think stock voltage is 1.06v looking at another generic BIOS. There is also 1.12v available.

(676/576) * (1.18/1.06)^2 = 45.4% more power, no wonder it's hot...
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