8800GT voltage mods

[scottc19]

oohms what are those other spots you modded. I see the Vmem and Vcore mod, but what are the others for/or control???

[2bb1]

Hey! Tried the volt-mod on my 8800GT today. But first, could you look at the picture added below; what is that thing? A capacitor?

[largon]

2bb1,
You mean this one? It's a resistor.


Why?

[oohms]

Hey guys, im going to need some help with this one. Basically i found a number of mosfets on the board whose output voltage i can adjust. But 3 voltages are unknown to me:

red 1.10v Vcore
brown 2.00v Vdimm
yellow 1.79v Tiny mosfet
blue 5.05v Large mosfet (Looks like 5V supply)
green 2.44v Large mosfet, near front of card
gray 1.18v Large mosfet

[HitandRun]

Ok, I think I got confused The 3 spots are the alternatives and I can just solder there with another wire to ground? Why did you chose soldering on the IC anyway? It's so difficult and tiny.

Yes the 3 spots are alternatives where you can solder onto! I had to solder to the pin on the IC because nobody knew where the pin # 22 tracing goes to and it is not possible to put your meter lead to the pin on the IC and look for another spot on the backside of the card to solder to. With the wire soldered to the pin it was much easier to find alternative soldering places for the mod. Let me know how it works out for you as I’m fighting the freezing on my card. I talked to Largon (BIG THANKS TO HIM FOR SUPPORT) and he says that the freezing is not OVP or OCP so I’ll have to sort it out on my own. I won’t have too much time during this weekend to test as I’m testing my new Giga EX38 board but next week I’ll be back on the game.

[largon]

oohms,
DVI uses 5V on some pins, 1.79v could be vDDQ since yours is a non-reference card. 2.44v might be there for s-video signal source. No idea about the "1.18v" though...

[oohms]

oohms,
DVI uses 5V on some pins, 1.79v could be vDDQ since yours is a non-reference card. 2.44v might be there for s-video signal source. No idea about the "1.18v" though...

Thanks!

Maybe 1.18v is Vref for the gddr3?

[2bb1]

2bb1,
You mean this one? It's a resistor.


Why?

Yes that one!
It fell off while I were modding. So I "cancelled" the vmod to check if the card were still working; and it does. How can this be if I've removed a resistor? Can it be this way, or should i "mount" it back on?

[oohms]

Ok i found out a few things today.. (went and downloaded the datasheet for the samsung ram it uses)

- Vdd = Vddq (Damn cheapskates )

- Vref is controlled by a voltage dividor as such:


Now im just clarifying, i reduce the resistor between Vref and Vdd to increase Vref right?

(The only bad thing about this is that each chip has 2 separate Vref points, so 16 modifications in total )

edit: as it is, that will provide Vref = 51% of Vddq, instead of 70% of Vddq

[Demo]

Im interested in a vGPU mod on a Palit 8800GB 1gb edition, does anyone know to do it? pref the mods that i can make trace lines via conductive ink and place the VR there instead of soldering directly to the IC

[Hazaro]

I'm just dropping in again. I'm going to be modding mine again, first time ended badly... and well the 3 pin looks like it's a little safer

[jason4207]

Ok i found out a few things today.. (went and downloaded the datasheet for the samsung ram it uses)

- Vdd = Vddq (Damn cheapskates )

- Vref is controlled by a voltage dividor as such:


Now im just clarifying, i reduce the resistor between Vref and Vdd to increase Vref right?

(The only bad thing about this is that each chip has 2 separate Vref points, so 16 modifications in total )

edit: as it is, that will provide Vref = 51% of Vddq, instead of 70% of Vddq

Are you trying to isolate the memory voltage from the memory controller voltage? I was told that wasn't possible, but if you get it working I'm very interested to try it!

[scottc19]

Are you trying to isolate the memory voltage from the memory controller voltage? I was told that wasn't possible, but if you get it working I'm very interested to try it!

This would, at least in theory provide higher memory clocks correct? Because the memory controller wouldn't be overvolted, but the memory could attain more voltage for higher clocks, at least for the quimoda?

Also does anyone have a looser memory timings bios that they could give me?

[Demo]

I think Galaxy claimed that the 3 phase power needed extra juice compared to the 2 phase PCB design. I might be wrong on this one!

My Palit 8800GT is using 3phase and only has 1 PCIe power connector though.

[Demo]

Lemme know if you need a closer view of a specific area, though my camera is a stone age point and shoot DSC-P200 sony.

Heres my 8800GT 1Gb Palit brand, where do i solder for a vGPU mod ?

[scottc19]

Got my 88800gt back from rma, stress tested it stock and the stock mem 950mhz was stable! So I out on my water block and modded it up. I set it to 1.5v and 1.84vmem like my other card and boot up w/sli bridge in. I get into xp and make sure all my rivatuner overclock stuff is off. Then I open the nvidia control panel and click enable sli. Screen goes black and pc immediatly restarts. I load up xp again and do the same thing, it restarts again, this time won't get past xp loading screen. I unmod the Vmem buck and take my other 8800gt out and put this one in the default slot. I turn it on and I get white and green boxes everywhere that move in post screen. It looks like heavy artifacting, but it has to be stock clocks, because i did not mod bios and I took my Vmem buck mod off, so It is completly stock... Maybe tomorrow I'll take the Vcore mod off and try it, but I doubt that will fix it, but i'll give it a shot. In the mean time anyone have any ideas????

[os008]

Are you trying to isolate the memory voltage from the memory controller voltage? I was told that wasn't possible, but if you get it working I'm very interested to try it!

This would, at least in theory provide higher memory clocks correct? Because the memory controller wouldn't be overvolted, but the memory could attain more voltage for higher clocks, at least for the quimoda?

Also does anyone have a looser memory timings bios that they could give me?

It would be great if someone could figure out the memory controller thing.

Also, is there any benefit from loosening the memory timings?

[largon]

Im interested in a vGPU mod on a Palit 8800GB 1gb edition, does anyone know to do it? pref the mods that i can make trace lines via conductive ink and place the VR there instead of soldering directly to the IC

http://www.xtremesystems.org/forums/...&postcount=532

[oohms]

Are you trying to isolate the memory voltage from the memory controller voltage? I was told that wasn't possible, but if you get it working I'm very interested to try it!

Vref is the voltage which is used by the ram to determine if a signal is 1 (high) or 0 (low).

Usually this is about half of Vdimm, but the GDDR3 specs and the samsung datasheets say that it should be 70% of Vdimm. Its actually 51% of Vdimm, so hopefully soon ill change it to 70% and see how it affects my ram overclocks.


I haven't looked into the memory control voltage, since there isn't much info about it. At least one of the unknown voltages is used by the GPU though, so ill try adjusting them to see if it affects my OC.

[oohms]

Got my 88800gt back from rma, stress tested it stock and the stock mem 950mhz was stable! So I out on my water block and modded it up. I set it to 1.5v and 1.84vmem like my other card and boot up w/sli bridge in. I get into xp and make sure all my rivatuner overclock stuff is off. Then I open the nvidia control panel and click enable sli. Screen goes black and pc immediatly restarts. I load up xp again and do the same thing, it restarts again, this time won't get past xp loading screen. I unmod the Vmem buck and take my other 8800gt out and put this one in the default slot. I turn it on and I get white and green boxes everywhere that move in post screen. It looks like heavy artifacting, but it has to be stock clocks, because i did not mod bios and I took my Vmem buck mod off, so It is completly stock... Maybe tomorrow I'll take the Vcore mod off and try it, but I doubt that will fix it, but i'll give it a shot. In the mean time anyone have any ideas????

Did you measure the voltages when this happened? You also might have accidentally knocked a small component off it, has happened to me before

[jason4207]

Got my 88800gt back from rma, stress tested it stock and the stock mem 950mhz was stable! So I out on my water block and modded it up. I set it to 1.5v and 1.84vmem like my other card and boot up w/sli bridge in. I get into xp and make sure all my rivatuner overclock stuff is off. Then I open the nvidia control panel and click enable sli. Screen goes black and pc immediatly restarts. I load up xp again and do the same thing, it restarts again, this time won't get past xp loading screen. I unmod the Vmem buck and take my other 8800gt out and put this one in the default slot. I turn it on and I get white and green boxes everywhere that move in post screen. It looks like heavy artifacting, but it has to be stock clocks, because i did not mod bios and I took my Vmem buck mod off, so It is completly stock... Maybe tomorrow I'll take the Vcore mod off and try it, but I doubt that will fix it, but i'll give it a shot. In the mean time anyone have any ideas????

I can't specifically diagnose your problem, but hopefully it'll work fine after you remove or at least turn down vGPU.

I wanted to comment on your vmem mod, though. 1.84v may be ideal for 1 card, but it varies from cad to card, so you need to do some testing. My first card liked 1.84v, but the 2nd one only liked 1.8v.

[2bb1]

Yes that one!
It fell off while I were modding. So I "cancelled" the vmod to check if the card were still working; and it does. How can this be if I've removed a resistor? Can it be this way, or should i "mount" it back on?

Can anyone tell me if it's OK that the resistor is gone?

[goranm]

Heres my 8800GT 1Gb Palit brand, where do i solder for a vGPU mod ?

There you go.

[Demo]

Thank you!

[scottc19]

I took all the mods off the card and tripple checked that all the components were there... It looks exactly like stock, I even compared it to my other card. yet it still has the same problem... This card just died somehow ><

Maybe my motherboard fried it somehow with the other slot?