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MONKEYMAN 10th April, 2006 06:12 AM

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.

Got EpOx 10th April, 2006 03:10 PM

Thanks for sharing this mod with us Monkeyman i'm sure some of our fellow 7800GT owners will be pleased :thumbsup:

Daniel ~ 10th April, 2006 05:35 PM

Copied ito our FAQ! Many thanks Monkeyman!

XeroHouR 11th April, 2006 09:51 PM

any idea if these mods will work on a 7900GT or GTX because IIRC they are just the same card with a new fab process, which means less heat and higher clocks, so, more volts will be more heat, back to the 7800 levels, but faster clocks?

MONKEYMAN 12th April, 2006 09:03 AM

will not work on a 7900gt as they are a different design, methods for these cards are mainly hard-mods using conductive ink/variable resistors.

XeroHouR 12th April, 2006 01:13 PM

since the last 3 or so gens of nvidia cards have been able to increase voltage through a bios flash, I'm sure its simply a matter of time anyway :)

danrok 13th April, 2006 02:52 PM

You're up in lights, MONKEYMAN!

muttley9 14th April, 2006 04:29 AM

Following the directions got me these results:

Before Bios Soft vMod
3D Mark 2001 SE
Score: 24090
CPU: 2600 Mhz
7800 GT Core: 470 Mhz
7800 GT Mem: 550 Mhz

After Bios Soft vMod
3D Mark 2001 SE
Score: 24874 (+784)
CPU: 2600 Mhz
7800 GT Core: 490 Mhz
7800 GT Mem: 570 Mhz

This just using the built in OC in the nVidia Control Panel.

Thank you, Monkeyman. :)

tiamat63 14th April, 2006 06:41 AM

Good god man, dont even bother using 01SE as your reference, you should have been judging my 05 or 03 at the latest. The problem is 01 is highly CPU dependant. The difference between my 7800GT and X1800XT on 01SE was next to nothing when I upgraded...however 05 saw significant gains.

MONKEYMAN 14th April, 2006 09:03 AM

Excellent!, Seeing as my card is still running at very reasonable temperatures I am more than likely going to attemp a hard-mod on this card, Im going to work on the memory first as I know that the particular version of memory used on these cards has a fair amount of slack left when it comes to voltage increases, I am hoping to aim for a 15% increase on the current memory speed and I will be happy if I can get my core speeds upto 520mhz+.
However I will need to work within the current constraints of the stock cooling which means that even with optimal airflow within the case I an unlikely to be able to run more than 1.6v (a 0.2 volt increase on stock), raising the voltage above this level would require water/phase change cooling and is generally detrimental to the lifespan of the card.

Muttley9: You seem to have hit exactly the same end result as me, glad it worked!

Samuknow 25th May, 2006 07:54 PM

Did this on my vanilla 6800 to 1.5 .Worked great...

MONKEYMAN 26th May, 2006 07:43 AM

Glad it worked!

dsio 26th May, 2006 07:53 AM


Originally Posted by Samuknow
Did this on my vanilla 6800 to 1.5 .Worked great...

1.5 on a 6800 is actually a bit high mate. That voltage is for a 7800GT

MONKEYMAN 26th May, 2006 08:04 AM

Yeah, should have mentioned that lol, 1.5v for a 7800GT is not even pushing things with the stock cooler on, your 1.5v on your 6800 is like 1.6/1.7v through a 7800gt.

You might push out too much heat for your cooler or damage your card, the 6800 series cards did have a sudden death problem with higher voltages on some models.

Samuknow 26th May, 2006 11:47 AM

It has been lite this for over a problems at all.....It is a Leadtek with that really big heatsink on it....It will be WC soon....I did 1.4 first and got good results with minimal heat increase.....This is the thread I started when I did has been great

Thing is I asked and aksed about this before I tried one piped up then...

dsio 26th May, 2006 12:04 PM

Well, I did, and said the 1.44V I was running was as high as I considered safe, but its your card and your choice. If you are watercooling soon, I wouldn't worry, but I would keep a close eye on temps, and force fan always on with an 80-100% duty cycle.

Samuknow 26th May, 2006 12:25 PM


Originally Posted by dsio
Well, I did, and said the 1.44V I was running was as high as I considered safe, but its your card and your choice. If you are watercooling soon, I wouldn't worry, but I would keep a close eye on temps, and force fan always on with an 80-100% duty cycle.

the fan is set to stay on @ 75 normal and 100 Performance 3D.
I'm not getting on to anyone here just stating that no one stated that this could be fatal...

My temps do stay ok though...44C now just sitting...Never seen above 56C when gaming...

dsio 26th May, 2006 12:32 PM

Oh, well there's nothing wrong with those temps mate. I take it you have a cold climate?

In my computer room, 45C is the ambient room temperature with the air con off. 30C with aircon. We are having a cold snap now, so it isn't so bad right now though.

Samuknow 26th May, 2006 01:05 PM

Yea I keep it quite chilly in the house....Not for me or my family but for my

Stays about 23C ambient is about 25-30 depending on the time of day.

BTW I have managed to get to 415/875 with stock cooling...hopefully higher once I WC it...

Sorry for running away with this thread.....:rolleyes:

MONKEYMAN 26th May, 2006 01:55 PM

I got mine upto 410/920 with stock volts and cooling(some model as yours) so with a bit of extra voltage behind you , I reckon you can get the core a little higher, the memory is only rated for about 700mhz ish.

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