8800GT voltage mods

[jason4207]

The mod is good for about 20-40MHz. I was able to tighten up my timings as well. See my other comments below.

Both my GT and GTS have Qimonda RAM chips. I wish I had some Samsung's! The way I understand it is that both the vRAM, and the memory controller are fed from the same voltage line. The vRAM by itself should respond better to more voltage, and I think the specs have them listed up to 2.5v. The problem arises b/c the memory controller doesn't respond well to voltage. So, if you start raising the voltage you are just making the controller crash, and that is seen as the memory avalanche.

There is a definite 'sweet spot' that I was able to find on both cards. The GT liked ~1.84v, and the GTS liked ~1.96v iirc. Dialing in that sweet spot actually had me making the smallest turns possible on the VR to find that spot b/n memory avalanche (red or green crap all over the screen) w/ lock-up if the voltage was too high, and just plain lock-up if the voltage was too low. Those last few changes I made to the VR in finding the sweet spot didn't even register on my DMM, but they did allow me to pass 8 loops of 'Battle of Proxycon' form 3DMark03 at 1 higher notch on the slider. On my GTS I started at 1062 stock to 1101 w/ the mod. That was pretty easy, but it was tedious work to get 1107. On my GT I was able to go from 1026 stock to 1056 w/ the mod, but had to go back down to 1044 after I increased the core/shader clocks and voltage.

I forgot to mention this above, but a big thanks goes out to Viper John for all his highly informative help he gave me via email. And also to all you guys here like Largon who helped to find these mods. I'm not sure who all found what, but kudos to you gentlemen. My knowledge has increased 10 fold in the past couple months as I've researched, prepared, and then accomplished these mods.

Thank you!

[scottc19]

My 8800gt wouldnt hold 950 without crashing... 930 was stable... I found my sweet spot to be 1.78vmem... this enabled 1000 to be stable 8 loops through the proxcon in 3dmark 03

[Pacha]

I just bought my 8800 GT, Twintech, reference design with new fan.

no gaymonda, it has Samsung chips


I did the vgpu mod, and I must say I did pretty bad this time. the little metal button under the primarion chip just came out with the wire when I pulled it accidentally, I tried to put it back but without great success, so in the end I almost owned everything in this area, indeed the abrasive grease I use also add some brown color to the solder (see the ground one) but still... it looks pretty gay


anyway, it works like a charm

[jason4207]

Do you plan on doing either of the vmem mods? I'm curious if you can get any better results than the Qimonda chips at higher or lower voltages.

I've got another GT sitting here..eVGA. I'm hoping it has Samsung chips, but I'm not holding my breath. I'll be taking it apart here in the next few days. I think I'm going to put the HS from my GTS on it, and just up the volts to 1.25v idle or so. Also, tweak the RAM, and throw OCP on there just in case I want to get crazy w/ it later.

[Pacha]

Do you plan on doing either of the vmem mods? I'm curious if you can get any better results than the Qimonda chips at higher or lower voltages.

I've got another GT sitting here..eVGA. I'm hoping it has Samsung chips, but I'm not holding my breath. I'll be taking it apart here in the next few days. I think I'm going to put the HS from my GTS on it, and just up the volts to 1.25v idle or so. Also, tweak the RAM, and throw OCP on there just in case I want to get crazy w/ it later.

I must say I'm quite upset of soldering on tiny electrical parts right now.
I saw on the samsung chips datasheet that it is rated at 1.9V ±0.1V so it may be overvolted at 2.0V (didn't checked it with mm though, I just forgot), like qimonda is.
My previous vdd mod on samsung chips never turned very useful, it always went bad creating artifacts like mad after some time. However, it helped to increase vdd to get a little bit higher clocks so I hope the stock voltage on this one will help to get good clocks.
Besides, I'm rather focusing on fabricating a new fixation for my wb and cutting sinks.

[jason4207]

Fair enough. I'd like to see how well your memory OCs at stock, though, if you don't mind. Can you make sure to test w/ the BoP-03, and CF-05 loops, so I can get a baseline of how your Samsung's do against my Qimonda's?

[Pacha]

sure I'll do some 2k3 and 2k5 loops, but I'll post it only when I'll have finished to prepare the card, and for now I have to buy some Ø 2 mm * 50 screws or build it myself with nuts and thread stalk, and also a square bar, my current one is too short.
I'm also waiting for the fan I ordered to put on the mosfets and some rams, plus I don't have my saw right here to cut the nb sink for the other rams so it won't be before the end of the week

[jason4207]

sure I'll do some 2k3 and 2k5 loops, but I'll post it only when I'll have finished to prepare the card, and for now I have to buy some Ø 2 mm * 50 screws or build it myself with nuts and thread stalk, and also a square bar, my current one is too short.
I'm also waiting for the fan I ordered to put on the mosfets and some rams, plus I don't have my saw right here to cut the nb sink for the other rams so it won't be before the end of the week

No rush.

Do you paraglide? I've been doing it for almost 14 years, but I'll admit I haven't been up much in the past couple of years. Hopefully, this summer I can get some flights in.

[Hazaro]

Pacha! Your poor poor GT!

[Pacha]

Pacha! Your poor poor GT!

what do you mean?

[Pacha]

No rush.

Do you paraglide? I've been doing it for almost 14 years, but I'll admit I haven't been up much in the past couple of years. Hopefully, this summer I can get some flights in.

Indeed yes, this is me on my avatar with my Advance Epsilon 5. I'm much more a beginner than you if you've been flying for 14 years, I've only 105 flights, though I've been flying for about 7 years.
I fly during summer exclusively in the Alps of France (around Annecy if you heard about it). I'm flying this summer too

[Robilar]

I have a pair of asus 8800gt. I took off the stock coolers for a pair of thermaltake duorbs and saw that there is an uncovered jumper in the upper right hand corner of each card.

any ideas what this does?

[Nosfer@tu]

The mod is good for about 20-40MHz. I was able to tighten up my timings as well. See my other comments below.

Thx mate

[XSS]

Can any here make a mod for my card i will give more core an mem !
It is a Gainward 88GT non reference




Mercie

[natedog420]

its the same as the mods in the first post. everything looks to be in the same spot for the most part. look at the first post. theres a pic there.

edit: the vgpu ic seems to be in the right spot just labeled different. the memory ic is right below it and looks to be the right 2 spots. just figure out witch way ur vgpu ic id facing and use the first pic so u get it right. its a little different so look close.

[hias]

hey guys,

i have a gainward 8800gt, stable @ 830/2023/1000 (62.92.12.00.04 bios and about 1,305V vgpu in vista). still on default cooler, but soon on accelero s1

my mem timings are very tight, but my qimonda chips are doing quite bad, i think.

well, i read somewhere here, that these qimonda chips perform better @ 1,9V.
Does anybody know a vmod, to lower vmem from 2,0V to 1,9V ?

Greetings

[jason4207]

hey guys,

i have a gainward 8800gt, stable @ 830/2023/1000 (62.92.12.00.04 bios and about 1,305V vgpu in vista). still on default cooler, but soon on accelero s1

my mem timings are very tight, but my qimonda chips are doing quite bad, i think.

well, i read somewhere here, that these qimonda chips perform better @ 1,9V.
Does anybody know a vmod, to lower vmem from 2,0V to 1,9V ?

Greetings

Go back to my post 592, and look at the vmem buck mod. Use a 50k VR, and tune to max resistance to start. You'll have to play around to find the sweetspot. Read some of my previous posts on the matter. This last GT liked 1.8v, the previous liked 1.84v, and some guy said his liked 1.78v.

[opc]

Hi Guys

I just finished the Vgpu mod on my two SLI’d XFX 8000GT’s late last night, and I thought I’d share my results here. I took a bunch of pictures along the way, and I have a pretty extensive electronics background, so if there is enough interest I can post up a full step-by-step guide with pictures. It seems like there are a handful of people on here who really know their stuff, and another handful of people who shouldn’t be allowed near a working toaster, let alone a $300 video card. Hopefully I can write up a guide that could help the people in between

Now for the results:

Pre-mod I had what amounted to a set of dud cards. I’m not sure if the SLI configuration makes things less stable, but the pair of cards couldn’t reliably break 675MHz. Both cards were on DD Maze5 waterblocks with idle temps between 18-22C and load temps between 28-30C with the help of a dryer vent and a very cold Canadian winter. Basically, there was no excuse for their poor results. I actually returned one of the cards after finding out that it couldn’t even run reliably at the stock 900MHz mem clock. I got the exact same pixilated crashed discussed earlier in this thread. I had to scale the mem clock back to 870 just to get reliable play time in Bioshock.

The Vgpu mod has certainly been a saving grace for both these cards. I’ve run the voltage up to a conservative 1.276V measured and adjusted under load from ATItool. Both cards are currently happy at 800gpu/1000mem, which is exactly where I wanted them to begin with. I’m sure they could go higher, but to be honest, I just wanted them to perform reliably at a solid clock speed. I’m not willing to trade stability for another 60MHz.

My core temps have gone up 1C at idle and 2C under full load, which still keeps them below 35C at the highest. I have a bunch of ram-sinks all over the cards, covering the memory and mosfets, and a single 80mm fan blowing over the power supply end of the card. Everything is cool to the touch, except the RAM at the far end of the card, and the little SOIC chip on the bottom of the card, which is pretty toasty as well.

I was hoping that by keeping the cards below 1.3V under load, I could avoid the OCP mod, and so far it looks like I’m alright. I’ll perform some longer stability tests and report back on the outcome. I have a pile of SM resistors hanging around, so I guess if worse comes to worse I might give the OCP mod a shot.

Now, I have a quick question for anyone who is familiar with 3DM06. I’m finding that my scores for the video cards are really sub-par compared to what I’ve been seeing on here. I did a run with a single card fully stock, and the 2.0/3.0 scores were 4815/4915 respectively. At 800/1000, a single card pulls a more respectable 5650/5860, but I was expecting to be well into the mid 6000’s at that clock speed. What’s even worse is that the SLI’d pair turn in even more pathetic results. With two cards at 800/1000, and a Q6600 at stock clocks, I get an embarrassing 13696. I’ve had the processor up at 3.2GHz, and that helped quite a bit with the overall score, but the SM2.0/3.0 scores are still poor for the cards, regardless of where the processor is at. I’m running a 122-CK-NF63-TR motherboard with the latest 169.21 drivers. (there’s a 122-CK-NF68-A1 in the mail right now, so that should help with the Q6600) Any suggestions would be welcome!

[natedog420]

very nice man. very clean looking.

[hias]

@ jason: thanks. mod works great
only have a very bad vr here at the moment (one or two turns). can't find my precise vrs with 30 turns....
btw, i think a 25kOhm VR should also do it if you want vmem < 1,9V

@opc: strange.... do you have all settings @ default in your driver settings?
will give you quite bad results if you have force 16x AF or 16xQ AA
my single gt does 6878 sm 2.0 and 6242 sm 3.0 @ default settings @ 837/2104/1026, and 800/1000 should be close to that.

[largon]

Can any here make a mod for my card i will give more core an mem !
It is a Gainward 88GT non reference

I'm going to need a clear macro shot covering just the area of the vGPU and vMEM controllers (RT8802A and RT9259A respectively) in order to see the controllers' pin and PCB traces. After that, some measurements.

its the same as the mods in the first post. (...)

The controller chip is a totally different IC from a different manufacturer so it's very likely the mod 1st post doesn't work.

i have a gainward 8800gt (...)
Does anybody know a vmod, to lower vmem from 2,0V to 1,9V ?

Is your card the same as XXS' card?

Go back to my post 592, and look at the vmem buck mod. (...)

Again, it's likely a different controller.

[Pacha]

largon, just let me ask you how do you figure all the mods for the different PCBs? I guess you have an advanced knowledge in electronics and usually try to find out how the circuitry work seeing the datasheets on manufacturers' websites, and then find out how to mod it. At this point, what do you do exactly do to know what to solder and such? just calculate the theorical // res after adding one at the good place and then the new voltage?

Or maybe you have a buddy who is electronic engineer for nvidia?

[XSS]

So here are a any Pictures , better macro i can´t make i have a Canon Z710















XSS

[largon]

Pacha,
It's really quite simple to device a vmod, even someone like me with just a basic knowledge in electronics 'n' circuits can do it - I guess some sort of an obsession for electrical things and miscellaneous gadgets is required too.

Simply put, most phase controllers regulate the output voltage via sensing the voltage through an array of resistors. One just needs to find where these resistors are located on the PCB and then solder a VR into the resistor network so that the combined resistance of the circuit changes, thus forcing the phase controller to adjust the output voltage of the power conversion phases.

Basically one just needs to:
1. find the controller's functional datasheet
2. look up the method the particular IC uses to control the phase output voltage
3. look up the pin(s) the IC uses to sense the voltage it controls and trace the pin(s) to a sensible solderable location
4. do some resistance measurements (or have someone do it for you) to determine the appropriate VR rating that makes the mod possible (resitance of multiple parallel resistors - very simple calculation)

Lol, I wish I had buddies at nV.

[jason4207]

@opc: Nice work man! A hot glue gun is on my list of goodies to get. I've been using strips of double-sided sticky tape for now. Check out my pics in post 592.

OCP can possibly kick in if you get a little closer to 1.3v. You might be fine. Try running AquaMark3. At the end before your score is produced the current spikes, and you'll know if you need to do the OCP mod.

Very nice choice in beverage! Chimay Blue Label is an old favorite of mine as well as many other Belgium Beers.

Try setting nVidia control panel to 'Performance'. Try running another benchmark like the Crysis one, and see if you see more improvement w/ higher clocks and SLI. Also, are you on VISTA or XP (32 or 64)?


@hias: I didn't think about it before, but if you have a non-reference board then you might have to wire it a bit differently. Thanks goes to Largon for pointing that fact out.


@Pacha: The way to figure it out is also briefly discussed here at post #23. I'm in the same position as you. I just started modding these cards. I have a much better understanding of why it all works now, but I'm still trying to figure out the discovery process.


@XSS: I have a cheap digital camera, and I've found it can take pretty good macro shots if I do a few things. Get lots of lighting, and don't use the flash. Get a bit further away from the object, and use the optical zoom (this allows the camera to focus better). Steady the camera on an object (tri-pod is ideal), and if possible use the timer so that you are no where near the camera when it shoots. That way no vibrations are transfered to the camera. Hope this helps!