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Old 10th April, 2006, 06:12 AM
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Modify your 7800GT BIOS!

After getting the best airflow possible around my XFX 7800GT I found was able to achieve a maximum long-term overclock of 470/1150, this is about on par with what most people are obtaining with this card but I wanted to get everything I could out of it, if you have a 7800GT and want to get a few more MHz out of it then read on.....

Most of you have probably heard about various hard-mods that you can perform on your graphics card, whilst component values vary from card to card they all basically involve the inclusion of a variable resistor so that the voltage across the core and/or memory is increased/decreased depending on the chosen value of the resistor.

These methods are often very effective at improving the maximum stable overclocks obtained, however they are also a very easy way to ruin your hard-earned card. Some excess solder creating an unwanted bridge to another component or a variable resistor set too high upon initial testing can render a card useless.

Hard modding also usually requires the use of high performance cooling such as water or phase change due to the much higher voltages raising thermal output drastically.

The following guide is a less effective method in that it will yeild a lesser gain in performance than hard-modding, however it is less risky and very easy to return to its orignal state if no gains are realised. It involves changing values in the BIOS of your card to increase the 3D performance mode voltage from 1.4 volts to 1.5 volts an increase of just over 7%.

In most cases the stock-cooler on the card is more than capable of dealing with this slight increase in temperature and there are no known major issues on the 7800gt cards with slightly increased core voltages leading to failure as there was with some 6800 series cards.

***Please Note:*** Some cards may not achieve any performance gain through this mod, in these cases it is recommended that you return the card to its original state, also some models of card (including the XFX 7800GT with the black PCB) will not allow the voltage to be changed even thought the BIOS entried are modified, it is recommended that you do not attempt this mod on this card. All modifications are done at your own risk and should be performed with no overclocks running on your system, you can consider your warranty voided, if this damages your hardware the responsibility is solely your own.

You will need: Nibitor 2.8(available on AOAfiles), Nvflash, Floppy disk, spare pci card for worst case scenario.

First of all install and open Nibitor, on the opening screen go to Tools-Read BIOS-Select device

Then Tools-Read BIOS- Read into NIBITOR

Click the voltages tab, tick the "Extend voltage table" box and change the 3D value to 1.5

Click Tools-Voltage Table Editor

Rearrange the table until it looks like the one below

When you return to the voltages tab and then the "VID Mode" tab it should look like this:

Save your new modified bios as newbios.rom

Once you have performed these steps place NVFLASH, CWSDPMI and newbios.rom onto a bootable floppy disk, restart your pc, boot to your floppy drive and type the following:

nvflash -r
nvflash -4 -5 -6 -A -y a:\newbios.rom

Your core 3D performance mode voltage should now be 1.5v and you should notice a small gain in maximum stable overclock, mine now auto detects at around 500/1150 a gain of around 30mhz.

Good luck, and if you decide to try this always remember to backup your orignal bios (i.e. save it in Nibitor before making modifications), even if you totally upset the flashing process you can still put pci card in and reflash with original BIOS or even perform a "blind" flash(essentially a normal flash but without being able to see the screen, you can also mod an autoexec file to perform the flash for you.).

Let me know if it works for you! this method also works on some other cards including some of the 6 series cards from Nvidia although I am not going to speculate which ones it would be beneficial for.
AM2 X2 4000

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