8800GT voltage mods

[os008]

Hi,
Since i shorted my 3850 , i had no choice but to go buy a 8800GT ... volt-modded, the RIGHT way this time, clean and tidy, put the iron on the wire ... voila soldered, didn't have to redo it a dizzillion times.

Well, a 200$ lesson on the 3850 :P.

Anyway, here're my results ... 1.12v got me ...



Using the Zalman VF700-Cu i had for ages, got me 40c idle, and 70c load.

For some reason i can get to 850 and 2000 shader, using 1.3v, but not stable, i think it's a heat issue, or maybe the powersupply, but i'm happy with what i got so far, i'm limited by the CPU anyway, so no need to be greedy.

Just a question though, my BIOS version is xx.92.16.xx.xx, i found the most recent BIOS is one from eVGA, version xx.92.A3.xx.xx, it has different clocks, and relaxed timings, i reset them to be the same as my card.

My question is ... would there be ANY benefit from using this newer BIOS, i included both BIOS'.

Thanks.

[zbomb5610]

I have 41 degrees load temp under ati tool with 832 core 965 memory. Seems stable at 1.35 load volts. I was wondering if 1.4 is a safe 24/7 load voltage as long as my load temps stay under 45 degrees? what is the highest recommended 24/7 voltage?

[os008]

I'm running 820 at 1.26v load, why are you using such a high voltage? (70 load temp)

[zbomb5610]

I'm running 820 at 1.26v load, why are you using such a high voltage? (70 load temp)

at 1.3 volts i couldn't run 830 stable. plus my load temps are only 43 max so far w/ pretty cool ambient temps, but even then i don't think it will go over 50.

edit* room is pretty warm now after running heater and it is about 49-50

[mundi]

CHAINTECH.8800GT.PCIe.512MB.Rev.01.zip
EVGA.8800GT.SS.PCIe.512MB.Rev.05.zip

If I only reflash this bios for my Asus 8800GT can I get more MHz Core ?
or I must do same mechanic hit to my vga (means voltmod etc.

[os008]

mundi, i'm posting those BIOS' for any expert to compare them, NOT as modified ones, do NOT use the e-VGA one, it has 1000 RAM clock, which is rumored to be buggy.

Please read my post with those attached files to know why i posted them.

Thanks.

[Droperidolum]

Here are the Palit 8800GT non-reference voltage mods and measure points
(developed by Nick Rimer and tested by Droperidolum (i.e. me ) from Overclockers.ru):

Please note before making this mod that you need to improove coling, especially on mosfet and coils, cause on 1.25V-1.30V it becomes very hot!
Some photos and default/overclock@1.36V/2.10V results screens you can find here (in Russian).
This mod also suitable to some XpertVision, Gainward and MSI non-reference cards based on this PCB design.
Good luck!

[S1mon-]

I'm kinda a noob when it comes to voltage and resistance, but how do you guys are able to go from 1,2V to 1,4V for the vGPU mod? You change the resistance from 500 ohms to 1K ohms? What is the required ohms to have 1,35V for exemple? Thanks

[zbomb5610]

I'm kinda a noob when it comes to voltage and resistance, but how do you guys are able to go from 1,2V to 1,4V for the vGPU mod? You change the resistance from 500 ohms to 1K ohms? What is the required ohms to have 1,35V for exemple? Thanks

you reduce resistance in order to increase the voltage. so you spin the variable resistor, spinning to reduce resistance will increase voltage. i don't know what the corresponding resistance is though for certain voltages, i just measured the voltage doing one turn at a time until i got the voltage i wanted. I fired up the system, checked the voltage, when i wanted more voltage, i turned it off, spun the resistor and then fired it up again to see what voltage change i saw. After you do a bunch of turns, the voltage starts to increase more rapidly.

[S1mon-]

you reduce resistance in order to increase the voltage. so you spin the variable resistor, spinning to reduce resistance will increase voltage. i don't know what the corresponding resistance is though for certain voltages, i just measured the voltage doing one turn at a time until i got the voltage i wanted. I fired up the system, checked the voltage, when i wanted more voltage, i turned it off, spun the resistor and then fired it up again to see what voltage change i saw. After you do a bunch of turns, the voltage starts to increase more rapidly.

Ohhh ok now I get it you gotta spin that little thing to play with the voltage I might try that mod but the resistor are so small it seems like i will touch something else and I'll kill my card... Is there a tutorial where I could see what kind of equipment I need?

[largon]

Here are the Palit 8800GT non-reference voltage mods and measure points (...)

Nice!

But, I doubt the "buck-mod" for lower vMEM will do any good on a board with Samsung GDDR3 such as the Palit one in the pic. Samsungs chips are whole lo different to Qimonda, they actually like higher vMEM.

[Droperidolum]

Nice! But, I doubt the "buck-mod" for lower vMEM will do any good on a board with Samsung GDDR3 such as the Palit one in the pic. Samsungs chips are whole lo different to Qimonda, they actually like higher vMEM.

That`s right. I had a 512MB card with 8 chips of Qimonda and now have 1024 with 16 chips of Samsung, so rising mod is reasonably to do on Samsung and lower mod - on Qimonda.
largon, can you help us to find out whats the second RT9259A needed for, except one that controlls Vmem?

[largon]

GDDR3 vDDQ comes to mind first.

edit:
Can't be the vDDQ as it appears vDD and vDDQ are fed from the same regulator...

[Droperidolum]

largon, but on the nearest, cond there are Vgpu...
And nearest coil is much smaller than others.
What can I do to know its purpose?

[scottc19]

Hey, just a thought for all you 24/7 gamers with these card volt modded and overclocked. I was able to have ati stable with no artifacting for at least an hour with 830core and 2200 shadder, but in certain games, speficially timeshift and f.e.a.r. I had to lower the shadder way down to 1900 and the core to 760, to get it to run through the whole game with out shutting down. For reference I'm usingv 1.33v idle, and 1.39 full load.

Also does anyone else still have the problem in vista where after you resume from standby the video card crashes after a few minutes, Im using vista x64, any help would be greatly appreciated.

[os008]

I had the exact same issue, was using 1.28v though, had to lower it from 850/2000 (stable in ATiTool), to 820/1900. Increasing the voltage didn't help, and in the end reduced it to 1.22v, which was the same as 1.28v in terms of stability.

Maybe it's just a heat issue, we might need a more extreme cooling system.

[scottc19]

What temp is yours mine idles in the low 30's and I think maxes out at 45, usually only hits about 42 tho.

[OverClocker_gr]

hi there.
A friend of mine has an Albatron 8800GT Short PCB




And i cant find anything about vgpu on that board.

Does anyone have a clue about this board?

[jason4207]

os008 & scottc19 - Have you guys done the OCP mod?

[scottc19]

no I didnt think ocp kicked in that low, does it? Also, how to do the ocp mod seems unclear, as someone stated that removing the resistor completly is not a good idea, and the only other method I have seen posted here was that of viper johns however, the picture that went with his post is no longer available. So does anyone have a picture or a clear explanation of what to do?

[largon]

I personally wouldn't recommend removing the "OCP resistors" (78X) completely - replacing those burned fets are a PITA. Luckily there's another way. The method described in G80 OCP -thread works on G92 based cards too. Basically it means you solder three resistors to the OCP circuit parallel to certain SMCs (surface mount capacitors).

It goes like this:

Note that only the two upper resistors are needed for G92GT as the reference PCB has two active vGPU phases.
Resistor value of 1.2kΩ is not set in stone, lower values cripple the OCP even further, but it is possible adding Rs of considerably lower value would interfere with the controller chip's ability to maintain balance between the phases. Higher value Rs are safe but the gained headroom becomes smaller the higher you go.

[largon]

Just finished replacing the burned mosfet.
The card didn't wake up.


Typing this on a G92GTS.

[jason4207]

no I didnt think ocp kicked in that low, does it? Also, how to do the ocp mod seems unclear, as someone stated that removing the resistor completly is not a good idea, and the only other method I have seen posted here was that of viper johns however, the picture that went with his post is no longer available. So does anyone have a picture or a clear explanation of what to do?

Yes it can. It can kick in around 1.3v (idle). Run AquaMark3 to bring out OCP. Right before the score displays the current spikes, and you can tell if OCP is holding you back.

VJ recommended ~4k value resistors to get an additional 25-30% more OCP headroom. That should be plenty unless you're going extreme cooling.

[scottc19]

Hey, thanks a lot largon and jason. I just did the mod and have completed a few tests at 810core 2214 shader, it seems stable wich is awesome! Now on to the next delimma my memory, my memmory wasnt stable to begin with I think the max i have run stably is 930 maybe 920, im doing tests now and sadly my default mem was 950. This is still the same unless the ocp mod has anything to do with helping this which I'm pretty sure it does not. Did anyone figure out how to lower voltage to mem or should I try to raise it. Or will I just have to live lower mem than stock? Any ideas appreciated.

[jason4207]

My vRAM wouldn't run stock either, and mine was 900 stock! I had to run 885 to get it stable through 8 loops of Battle of Proxycon 3Dm03. Luckily I caught the problem before doing any modding, and it is currently in RMA. I should be getting the replacement tomorrow!

Lowering the voltage to the memory has helped several people w/ the Qimonda chips.