7600GS Volt Mod with Pencil Trick

[Anthony Rogers]

This is my first post, so please bear with me, if I make any mistakes.

The Leadtek 7600GS runs at stock 400/400. This is a revision A1. The memory chips are Inifineon A HYB18T256161AF-25 WVV17892 0604.

This card was chosen because it was the cheapest 7600GS at the time on Newegg.com with dual DVI and a heatsink with a fan, not the passive heatsink. With stock fan and voltage, the most stable overclock was 485/485. Changes were made in 5mHz increments using Coolbits, and then the card was tested for artifacts with ATItool.

I couldn’t find any information on a volt mod for the 7600GS other than the post by SF3D in another forum, so that was used as a starting point.
http://www.xtremesystems.org/forums/...ad.php?t=96608

A multimeter was helpful in identifying the resistor that needed to be adjusted. In order to not make any permanent changes, the pencil trick was used along with the multimeter to measure the new resistance. The predicted voltage was then calculated to make sure that the voltage would not be too high, and the actual voltage was also measured to confirm. The predicted and actual values were the same.

Concerned that the DDR2 memory might be a limiting factor, I overclocked the memory first. Benchmarks were performed with 3DMark06 and are plotted further below. Memory does appear to be a limiting factor.

Test probes seemed to indicated that the stock memory voltage was 1.82V. However, another member, ocerwu found a technical paper that indicated that the stock voltage is 2.0V and the that max voltage is 2.1V. Due to this discrepancy, no point to measure memory voltage will be identified in the photos, until this issue has been resolved.

The resistor to change the memory voltage was also located and voltage was increased slightly, but this just made the system unstable and resulted in a lockup during overclocking the memory.

The 7900 GTX has overvoltage protection, so this was an initial concern. However, there was no trouble getting the gpu voltage up to 1.43V. Despite this high voltage, the card would not run stable past 600mHz. The maximum overclock that I was able to achieve was at 600/485 at 1.32V.

Temperature was measured at idle and under load with 3DMark06 using the nVidia driver, with the case open. All tests were performed with stock cooling. In a previous edit, the temps were measured in the max overclock with a Zalman VF700-Cu. Since the whole point of overclocking is to get the best price/performance, it doesn't make sense to buy a cheap card, then buy a $30 HSF. In addition, if one wanted to run the 7600GS in SLI, then the Zalman would take up too much space, at least on my motherboard in trying to accomodate 2 video cards. The stock HSF was used throughout the tests, with the exception that at max overclock, the HSF was lapped and AS5 was applied. (I don't consider AS5 or lapping the stock HS an exotic cooling solution, since sandpaper and a small tube of AS5 is pretty cheap and can be used over again on the CPU and northbridge.) Lapping didn't really make a difference with the stock cooler.

***Update 3***
Since the time of the first posting, a second and third card have been acquired. (A third card was obtained as the first card was fried accidentally). More extensive tests have been done on all cards with a max overvolt on the gpu of 1.5V each and of 2.9V on the mem. The goal was to find the limits of each card with the highest safest voltage. The results are quite remarkable. Each successive card has a higher overclock!

Clock Frequencies and Temperature Table


With the second card, the memory was more unstable when the gpu voltage was increased. A memory volt mod was done on the second card, which improved the memory overclock stability. Given, that the technical specs indicate that the stock voltage for memory is 2.0V, a calculation was performed to find a new resistance that would generate a voltage of 2.09V, below the max voltage of 2.1V. The voltage for memory is shown in parenthesis since these are still only theoretically derived from the tech specs. The increased gpu voltage and gpu overclock did make the memory more unstable on the second card, with a decreased max overclock of 460.

It appears that the active HSF does a fairly good job of cooling even when overclocked, as compared to the passive HS from other reviews at Newegg and below at HardwareZone. The HSF is also fairly quiet and not audible above the other fans in the PSU, Big Typhoon, and 120mm case fan.
http://www.hardwarezone.com/articles...856&cid=3&pg=9

SLI
The first and second cards were installed, and a reinstall of Windows XP was required, since the computer was unable to boot into Windows with the two cards. Once the nVidia driver was installed, the SLI setup was detected. Coolbits was installed.

Since, the writing of the first section, my computer experienced some instability. This was found to be related to a cpu overclock at 3.4gHz, and the system is now stable at 3.3gHz and tested with Prime95.

Even with a slightly slower cpu clock, the 3DMark06 results were phenomenal at 5155 at 665/460 on the first and second cards! (Tests have not been performed with the 2nd and 3rd card in SLI, but that score should be even higher.)

3DMark06 Plot


This is higher than a stock 7900GT score of 4109 at Guru3D. (However, an overclocked 7900GT will score higher.)
http://www.guru3d.com/article/Videocards/326/15/


VOLT MOD GUIDE FOR 7600GS
THIS WILL VOID YOUR WARRANTY

Items needed:
7600GS
Multimeter
Pencil

Back Of Video Card


GPU Zoomed In Area


1. Measure stock resistance with multimeter. Write down the stock resistance. This will be useful if you need to set your card back to factory settings.
2. Install card, turn on computer, and measure stock voltage with multimeter. (Touch the ground wire of your multimeter to the case and touch the probe to the contact point circled above). Write down the stock voltage.
3. Turn off the computer and remove the card and rub a pencil over the resistor circled above.
3a. Alternatively, install a 100K variable resistor at the point labeled New Resistor Here, with the other leg connect to ground. This resistor has 18 turns and is much easier to calibrate.
http://www.hobbyengineering.com/H1373.html
4. Test the resistance after the pencil mod using the multimeter.
4a. Alternatively, measure the new total resistance at the point Measure Total Resistance with the multimeter, with the other probe on ground.
5. The predicted voltage can be calculated by using the formula, V predicted = V stock * (R stock / R new)
6. Reinstall the card, check new voltage, and overclock.

Memory Zoomed In Area


1. Measure stock resistance with multimeter. Write down the stock resistance. This will be useful if you need to set your card back to factory settings.
2. Rub a pencil over the resistor circled above.
2a. Alternatively, install a 100K variable resistor at the point labeled New Resistor Here, with the other leg connect to ground. This resistor has 18 turns and is much easier to calibrate.
http://www.hobbyengineering.com/H1373.html
3. Test the resistance after the pencil mod using the multimeter.
3a. Alternatively, measure the new total resistance at the point Measure Total Resistance with the multimeter, with the other probe on ground.
4. The predicted voltage can be calculated by using the formula, V predicted = V stock * (R stock / R new). Assume that V stock is 2.0V for memory, and do now allow V predicted to exceed 2.1V
5. Reinstall the card and overclock.


With my mods, I installed some wires which were connected to some header pins on a small breadboard. This makes it much easier to remove the cards without worrying about extra hardware attached to the surface of the cards. I also put a switch on the breadboard, so that I didn't have to keep my cards overvolted all the time.

Feel free to post your results with this mod in this thread, along with comments or questions.

Good luck!
Anthony Rogers

[ocerwu]

Does Leadtek use Infineon MEM chips on 7600GS?

[MrFox]

Good work and welcome to guru3d

[Anthony Rogers]

Originally Posted by ocerwu

Does Leadtek use Infineon MEM chips on 7600GS?

Yes, they are Infineon chips. I've updated the post and included the Revision number as well.

Originally Posted by MrFox

Good work and welcome to guru3d

Thank you!

[ocerwu]

Where can I find the resistor which control the voltage of VRAM ?
Does the VRAM work well at 585MHz/1.91V ?

Thank you!

[Inteleron]

This is just VGPU mod rite? is there a VMEM mod? Anthony have you done both mods because your memory is running over a gig in your other post, and that seems quite high. Im considering on getting the XFX 7600GS XTREME which is 500/900 outta that box i wanna hit clocks similar to yours. Id liek to see both VGPU & VMEM mods.

[Anthony Rogers]

Thank you for pointing out my typo. I have corrected my post.

The max memory clock that was achieveable on my card was 485 in coolbits (or 970). DDR2 doesn't really clock higher than 1000. This is why the 7600GT uses DDR3. If people with the 7600GS are getting 450-500 in coolbits (900-1000), that's a great overclock.

At a higher voltage, and the RAM is likely to fry. (This has actually happened to people.) More voltage made my card extremely unstable and crashed the computer.

However, if one wants to take the risk and perform a small volt mod on the memory to increase stability, see the updated information in the first post.

The reason why the gpu can be overclocked further with a higher voltage is that the 7600GS runs at a lower voltage than the 7600GT. Keep in mind that the nVidia reference card for the 7600GS has a passive heatsink. By having lower voltage, a slower clock, and a quiet passive heatsink, nVidia is targeting a different section of the market.

If people want more performance, buy another 7600GS and run it in SLI. This is a great card, but there are physical limits to the DDR2 technology that cannot be overcome by simply adding more voltage.

Best regards,
Anthony Rogers

[Inteleron]

So maybee it worth shellnig out an extra 40$ on a 7600GT

[Anthony Rogers]

Originally Posted by Inteleron

So maybee it worth shellnig out an extra 40$ on a 7600GT

Well, it really depends on what you plan to do. Certainly, the more one spends, the better hardware and performance one will get.

One also needs to consider if they want to run a single card or SLI. Then it's not a matter of an extra $40, it's now an extra $80.

One also needs to consider if they buy the more expensive card, will it have the same price to performace ratio at stock or overclocked speeds? Just how much extra ability to overclock will that extra $40 buy?

You may want to consider reading the review at VR-Zone with the 7600GT Shoot-Out if you go with a 7600GT. Also keep in mind that although the Leadtek 7600GT card overclocked the best, each individual card's ability to be overclocked varies. Five out of the seven cards maxed out at 600mHz for the gpu.
http://www.vr-zone.com/?i=3551

Personally, I've ordered another Leadtek 7600GS, and I will overclocking it and running it in SLI. I've never had an SLI system, and I'd like to try it out. (See updated information in first post.) However, I don't really play a lot of games, and this is the most I'm willing to spend, all things considered. In fact, 95% of the time, I'll probably be running only a single card so that I can do my work using dual monitors. Part of the appeal for me is buying something relatively cheap and seeing how much performance can be squeezed out of it, i.e. Pentium D 805.

You really have to make your own decision. They're both great cards. You just have to decide how much you're willing to spend. Good luck!

Best regards,
Anthony Rogers

[ocerwu]

I download Infineon HYB18T256161AF-25 datasheet :
HYB18T256161_AF_rev1.3_2005-07-05.pdf
In this reference,it shows that the typical voltage of HYB18T256161AF is 2.0V.
(On page 62,even the max voltage can be 2.1v)

However,your measure of stock voltage of mem is 1.82V.
I guess that maybe the measuring point of mem is another one.

[Anthony Rogers]

Originally Posted by ocerwu

I download Infineon HYB18T256161AF-25 datasheet :
In this reference,it shows that the typical voltage of HYB18T256161AF is 2.0V.
(On page 62,even the max voltage can be 2.1v)

However,your measure of stock voltage of mem is 1.82V.
I guess that maybe the measuring point of mem is another one.

Great research! You're absolutely right, it does state that the core voltage is 2.0V. I poked around a bit more with my multimeter, but could not find any points at 2.0V. However, even if the wrong point was measured, the correct resistor was identified and the resistance was changed. This change in resistance resulted in no improvement. However, from this document, it is apparent that there is very little room to change the voltage, +/- 1.0V.

In addition, looking at page 75, it states that the max clock for the -25 (DDR2-800) is 400. So 485 is pretty good and has already exceeded the specified max by a great margin. I'm pretty satisfied with my memory overclock, and I'm not interested in pursuing this further until I get my second card. However, you are welcome to explore further.

The reason why the gpu overclock is so great in comparison is that the gpu is actually underclocked and underpowered. In the VR-Zone Shoot-Out, most of the 7600GT cards max out at 600, which is the same max gpu that I'm getting.

I'll leave my results the way they are, until someone definitively identifies a point to measure. If it's not correct, then it will be updated.

If anyone has any better luck measuring the Vmem, please post your results.

What kind of memory chips are on your card? What kind of overclock are you getting?

Best regards,
Anthony Rogers

[Inteleron]

Well I just ordered my EVGA 7600GT, and id like to bench agaisnt some of your max overclocks and me stock and see what we can pull off.

[Anthony Rogers]

Originally Posted by Inteleron

Well I just ordered my EVGA 7600GT, and id like to bench agaisnt some of your max overclocks and me stock and see what we can pull off.

Great! From reviews, the 7600GT runs 3DMark06 at 3096, from Guru3D.
http://www.guru3d.com/article/Videocards/326/15/
On a test setup with dual cpu at VR-Zone, that increased to around 3300.
http://sg.vr-zone.com/?i=3551

Those scores already beat the max overclock score of 2980 of my Leadtek 7600GS. The 7600GT scores even higher when overclocked.
http://sg.vr-zone.com/?i=3551&s=11
But this should be no surprise, as the 7600GT has faster memory.

It will be real interesting to find out how two of the 7600GS perform when overclocked in SLI. I'll try to post some results this weekend, after the second card arrives. It should come under the 7600GT SLI and maybe even above the 7900GT single. (See updated information in first post).

Best regards,
Anthony Rogers

[ocerwu]

MSI use the same memory too,but it can only work well at 920Mhz
Finally I had find the vmod reststor of memory,but it really made my system extremely unstable.Then I took a long time to reinstall my system.T_T
At last,it ran well at 660/460 and passed 3Dmark06 tests.I got a score of 3253(The score of stock frequency was 2585)
There was something wrong with my multimeter,so I could't measrue the resistances at all.
I think that the high GPU clock I get is just by lock.

[speekergeek]

Thanx Anthony Rogers for the info, i have been trying to find info on this card for a long time. hard to come by.
I brought my core voltage up to 1.7v first and monitored the temp for a while, it was idle aroune 101C, so i brought it down to 1.4 volts. my core speed is 650 stable. and my MEM speed is 454 topped out, can't go any higher there. I found the mem voltage sitting at .8 volts (or so i think) i brought it up to 1.1 volts but my system just didn't like it and kept restarting.
but if the mem is not supposed to be over 400 then i consider myself lucky with 454mhz.
My benchmarks didn't go up as much as I thought, but the gameplay is noticeably smoother on HL2. Temp is idle at 58C and tops out at 85C.
Now i am looking to up the fan speed, maybe a pencil mod will work. I don't even know if it is a single speed fan or not.

thanx again,
Mike

P.S. my card is a PNY 7600GS

p.s.s not that 3dmark06 is the greatest judge, but i gained 600 points on my score.... 2068 up to 2664 points

[Anthony Rogers]

Originally Posted by ocerwu

it really made my system extremely unstable.Then I took a long time to reinstall my system.T_T

I know what you mean. I've lost count of how many times I've reinstalled over the past 3 weeks, upgrading three computers at home and switching in and out two motherboards for each.

Originally Posted by ocerwu

I think that the high GPU clock I get is just by lock.

That is a really great overclock. I guess sometimes you just get lucky!

Originally Posted by speekergeek

Thanx Anthony Rogers for the info, i have been trying to find info on this card for a long time. hard to come by.

You're welcome. I'm very glad that my post has helped others.

Originally Posted by speekergeek

I brought my core voltage up to 1.7v first

Whoa! That's probably way too high. I've heard that around 1.5V is a safe max for the gpu.

Originally Posted by speekergeek

my core speed is 650 stable. and my MEM speed is 454 topped out, can't go any higher there. I found the mem voltage sitting at .8 volts (or so i think) i brought it up to 1.1 volts but my system just didn't like it and kept restarting.

Great overclock!

The memory should be at a higher voltage, more like around 2.0V. You were probably measuring the wrong point. The memory seems to be less tolerable of changes with the voltage, as everyone has been finding out. It seems that a small overvolt, <1V, may increase stability, but anything more will cause crashes. It's always good to make a backup before performing mods. I personally use a combination of Ghost for the boot partition and a backup data drive.

Best regards,
Anthony Rogers

[Anthony Rogers]

One last update. I've since tested both cards at a max voltage of 1.5V gpu and 2.09V mem and rerun the SLI results at 665/460. Note that the second card overclocked to 690 on the gpu at 1.5V!

I've also since killed the first card. The breadboard that I was using to switch the volt mod on an off touched the case and became grounded. This likely dropped the resistance to 0 and sent a surge through the gpu and fried it. I was actually getting ready to tape up the back so that this wouldn't happen.

I'm restoring from backups as I'm typing this on my 2nd computer. For some reason I can't simply switch from SLI back to single card because windows locks up and I have to restore an image that I kept when I had only the single card. Good thing for backups! But hey, this gives me time to post these updates.

This might be my last post for a while, unless I decide to shell out another $125 for another card. Well, at least I got to enjoy Oblivion last night. It was really nice being able to run most of the graphics at high. It did get a bit slow outdoors however at times even with SLI and overclocking, but definitely better than with a single card. FPS was generally consistently in the 40s outdoors, in towns, and dungeons.

*Update 2*
Okay, I ordered another card. I've now spent a fair amount on these cards, but I've seen the performance with two which was phenomenal. It was hard having just one card. The results for the third card have been posted

Best regards,
Anthony Rogers

[madmalkav]

I want to make some OC tests on my father-in-law XFX 7600GS card, but I have a little doubt: how much time must I scan for artifacts before trying a higher clock speed?

Thanks and sorry for the newbie question, can't find any info about that searching...

[Anthony Rogers]

Originally Posted by madmalkav

how much time must I scan for artifacts before trying a higher clock speed?

I found that artifacts showed up in the first 5 minutes of testing with ATItool if not sooner.

My experience with overclocking the gpu too high typically caused my entire computer to pause for about 1 minute with no response at all from keyboard and mouse and then it would continue as if nothing happened. This would happen with games, with 3DMark06, and with ATItool. Sometimes, I would get a message about artifacts from ATItool, but the pause seemed more common with the gpu overclocked too high.

With the memory overclocked too high, I would get a message from ATItool that there were artifacts. I was usually able to briefly visually see small artifacts in the rendered area in the ATItool window as well, which appeared to be small yellow dots.

If either was clocked far too high, the computer would simply crash requiring a reboot. Sometimes crashes can also corrupt Windows, requiring a new install of Windows.

When actually running games, I found that the video card was sometimes still unstable, causing 1 minute long pauses in the game. Backing down about 5-10mHz with the gpu overclock usually stablized everything for me.

Originally Posted by madmalkav

I want to make some OC tests on my father-in-law XFX 7600GS card

This should be obvious, but don't overclock anyone else's card, unless you're willing to buy a replacement if it dies or help them reinstall Windows if it becomes corrupt.

Good luck!

Best regards,
Anthony Rogers

[madmalkav]

This should be obvious, but don't overclock anyone else's card, unless you're willing to buy a replacement if it dies or help them reinstall Windows if it becomes corrupt.

Sure. And he loves to see how some messing around can get some extra power, not only with the computer, with almost everything, so I take care of his compuetr and he takes care of my car

Will try this weekend, thanks for the tip!

[Anthony Rogers]

Originally Posted by madmalkav

so I take care of his compuetr and he takes care of my car

Sounds like a great arrangement!

Originally Posted by madmalkav

Will try this weekend, thanks for the tip!

You're welcome. Good luck! Please post your results if you get the chance.

Best regards,
Anthony Rogers

[NobleKnight51]

I'm intrigued also. I'm considering two of these in sli with a moderate OC. Keep us posted please!

[greaterthenjake]

Is there a reason this was not done with a modded bios for the gpu voltages. i also have a pair of 7600's best i can do at stock voltages with my pn7600 gs's iis 517 core, 461 mem. i would rather soft mod than hard mod. if anyone has info on a modded bios or how to do one with a higher gpu voltage please pm me.

[icedragn43]

Originally Posted by greaterthenjake

Is there a reason this was not done with a modded bios for the gpu voltages. i also have a pair of 7600's best i can do at stock voltages with my pn7600 gs's iis 517 core, 461 mem. i would rather soft mod than hard mod. if anyone has info on a modded bios or how to do one with a higher gpu voltage please pm me.

im pretty sure he told you why, but it's because of the lack of an external power connector, it's already at max voltage through the bios, you need to hardmod it like this to get a voltage boost.

[Anthony Rogers]

Originally Posted by greaterthenjake

Is there a reason this was not done with a modded bios for the gpu voltages.

To be honest, I didn't try a modded bios. But I just tried it and it doesn't work. Stock voltage 1.10. Voltage after bios mod 1.10.

Best regards,
Anthony Rogers