8800GT voltage mods

[jason4207]

Do you think it's just the Quimonda chips that are benefiting from the vmem buck mod or Samsung and Hynix as well? I guess I could try pencil modding the memory to see if it responds to higher voltage and if not I could try the vmem buck mod. Kind of annoys me I'm losing like 50 mhz on the memory.

I have no idea about the Samsung or Hynix. I've been waiting for someone to post something. Your card is behaving like mine, though, so my 1st guess would be that vmem buck would help you. No way to know unless you try!

ok well i dont have the resistors i took off for the ocp mod i ended up losing them. i have an old motherboard. what do i need to measure to find new ones. can i just solder in one of the new ones since the stock ones are gone? i run 1.45 volts usually so i need the 1.2k like you say.

They are 78X. If you see SMR's on your MoBo w/ the same label they might work. If not maybe you can find them online. Only way to measure resistors on the Mobo is to remove them first.

You don't need 1.2k for 1.45v. 3.8-4.2k would work fine for that. You shouldn't have any issues until ~1.625v idle w/ 3.8-4.2k.

Its odd, I've been up to 1.45v on my MSI with no indication of the [s]OVP[/s] OCP activating. Doesn't seem to matter as my card won't clock any higher after 1.29v. What voltages are considered unsafe on these cards?

Have you tried running AquaMark3? That seems to be a good stress test for OCP.

[nvrmind]

I haven't tried AquaMark3. OVP doesn't seem to matter in my case since my card won't respond to higher than 1.29v. I was hoping to get the shader to around 2000, but 1825 seems to be it's limit. My card is one of the lower clocking cards I've seen on here. The voltage mod got me 90mhz on the core and 50 on the shader (800/1825). Not too bad, but I was hoping for more. Now if I can just figure out this memory issue.

I'll try the pencil mod first with these Hynix chips. If increasing mem voltage doesn't help, than I guess I'll go ahead with the vmem buck mod. I measured the voltage around 1.9v+.

[scottc19]

I haven't tried AquaMark3. OVP doesn't seem to matter in my case since my card won't respond to higher than 1.29v. I was hoping to get the shader to around 2000, but 1825 seems to be it's limit. My card is one of the lower clocking cards I've seen on here. The voltage mod got me 90mhz on the core and 50 on the shader (800/1825). Not too bad, but I was hoping for more. Now if I can just figure out this memory issue.

I'll try the pencil mod first with these Hynix chips. If increasing mem voltage doesn't help, than I guess I'll go ahead with the vmem buck mod. I measured the voltage around 1.9v+.

This seems really odd, how do you know that more voltage doesn't help,ie what kind of crashing are you getting. Does your card still read voltage after it crashes?

You don't need 1.2k for 1.45v. 3.8-4.2k would work fine for that. You shouldn't have any issues until ~1.625v idle w/ 3.8-4.2k.

So if you use 1.2k, what kind of headway do you think you will get then like over 2v? I used the 1.2k on mine for around 2 weeks without problems, but finally decided to rma since ram never ran stock. I am going to do this mod again on my set of 8800gt now and I guess if they can be pushed to 1.625, then it seems there isn't any point to go all the way down to 1.2k. Seems like 3.8-4.2 will do that trick. I am looking for 1.55max, so you think 4.2k will do or will I need the 3.8(ie is 1.625 with 3.8 or 4.2?)

[nvrmind]

I've gone up to 1.45v. 3D06 locks up above 800/1825. The strange thing is though I've been able to run 800/2000 without artifacts on ATI tool @ 1.29v for an hour and I can play CS:S without lock ups. Other times CS:S will lock up as well. My multimeter will continue to read the correct once 3DMark crashes, which is why I don't think it's OVP. I've had very inconsistent results so far. Temps are just fine, load is 40C running ATI tool.


**EDIT**

I was just able to pass 3DM06 @ 800/2000/950 @ 1.29v. Very odd. The only thing I can think that made a difference was changing a bios setting. My Biostar TA770 A2+ has a GPU setting in the bios that puts a wattage limit on the PCI-E slot. The default setting is 75W. I changed it to 135W. Perhaps that setting has made the difference, as a volt modded 8800GT is definitely eating up more than 75W. I'll keep testing and report back.

[EightyDuce]

nvrmind run AquaMark and see if it triggers OCP, thats about the easiest way of doing it.

[aussie-revhead]

Can you guys tell me how much difference there is between a vmodded GT and GTS at same clocks ? Which of these will score the highest in 3D06 ? I just want to know if its worth spending the extra $100+ per card .

Any help would be great.



Edit - looking at some of the clocks in this thread the GT clocks much better than my GTS , is there a brand/model of GT to look for ? One with better overclockability ? Better ram maybe ?

Cheers .

[EightyDuce]

GTS has more SPs than the GT so it should be faster clock for clock. Also, GTS will OC higher than the GT.

As far as brands go, they're all reference cards, for the most part, so should OC about the same. It's all about luck of the draw.

[jason4207]

So if you use 1.2k, what kind of headway do you think you will get then like over 2v? I used the 1.2k on mine for around 2 weeks without problems, but finally decided to rma since ram never ran stock. I am going to do this mod again on my set of 8800gt now and I guess if they can be pushed to 1.625, then it seems there isn't any point to go all the way down to 1.2k. Seems like 3.8-4.2 will do that trick. I am looking for 1.55max, so you think 4.2k will do or will I need the 3.8(ie is 1.625 with 3.8 or 4.2?)

I don't know the equation, but VJ told me 3.8-4.2k would give you 25% headroom. I know ~1.3v idle is where OCP kicks in, so 1.3 x 125% = 1.625v.

Largon said 1.2k gives you 50% headroom, so 1.3 x 150% = 1.95v.

I used 3.92k, but haven't gone any where near 1.625v yet, so I can't tell you for sure. I think you'll be fine for 1.55v w/ 3.92k or 3.8k if you want to be sure.

Someone correct me if my interpretation is flawed.

Can you guys tell me how much difference there is between a vmodded GT and GTS at same clocks ? Which of these will score the highest in 3D06 ? I just want to know if its worth spending the extra $100+ per card .

Any help would be great.



Edit - looking at some of the clocks in this thread the GT clocks much better than my GTS , is there a brand/model of GT to look for ? One with better overclockability ? Better ram maybe ?

Cheers .

It varies from card to card. My GT did a little better on the core, but the GTS did a lot better on the shaders. The GTS has 3 phase power, so my gut tells me it would handle the increased voltage better. Also, the GTS does much better on memory clocks. At the same vGPU, and w/ tweaked memory my GTS scores 1200 points higher in 3DMark06 than my GT. Plus you don't really have to do the OCP mod on the GTS (unless your going extreme cooling).

Ideally you want a GTS w/ Samsung memory. I have no idea how you'd be able to identify one, though. Perhaps a more recent date on the box would give you a better chance at getting the Samsung chips?