Finding 6800 PCIe VMod

[Cybercat]

Well I got another 6800 PCIe and I intend to get the best performance from it I can. So this thread represents a quest of mine to find the VCore volt mod for this particular card.

Unfortunately scanning the back of the card isn't an option, cause I got so much junk on there , so let me try to fill in as many of the chips on the back of the card as I can from a stock photo.



The list goes

57ATHXK
ACT0B

MAX8538
EEI 0421

2168
SC1

APM7313
XH38H (x2)

8546
EUB (x2)

I-R 506H
7J3V
F7832 (x3)

I-R 427H
9PGL
F7821

The biggest chip, and most likely to control all of the voltages is the MAX8538 chip. Here's a diagram, and a link to the PDF datasheet.



http://pdfserv.maxim-ic.com/en/ds/MAX8537-MAX8539.pdf

Now on the VR-Zone forums (which I can't access anymore for some reason), they said pin 12 was the most likely to control my VCore. As in turned out, with a 200k VR, it actually controls the VDDR. That would make sense since the PDF datasheet says the MAX8538 chip is a "DDR Power Supply". It's possible the MAX8538 doesn't control the VCore at all. That complicates things quite a bit. I've tried pin 17, which changes what I thought was the VCore (I found a read point on the card that reads 1.25V default), but even slightly changing this value ends up with graphical corruption.

I've also tried it with pin 7 and 10, resulting in no percievable changes.

So I really have no idea what controls the VCore. Any thoughts?

[Cybercat]

Well I went ahead and vmodded the memory. Went from around 860 to 910. No clue what the voltage is, but I don't feel like going any higher anyway. Don't have any RAM cooling, afterall.

Again, anybody with any insight they can think of, please post it. I know for a fact that this board has been visited by more than its share of hardware geniuses in the past.

EDIT: bah, damn artifacting in obscure demos and beta games. I figure the RAM's getting too hot anyway, so I took it off and just left the card at stock. I didn't like the fact that I couldn't monitor the VDDR anyway.

[Cybercat]

I bet with a volt mod to the core done correctly, this thing could do 500. The potential is there, I think.

BTW

[Cybercat]

*sigh* Guess all the knowledgeable people have left.

[MikalCarbine]

Good job , wish I could follow but I have a 6800gt

[SikaRippa]

Hi,

Sorry giving response *quite* slowly, but have been busy

--

I took a brief look to datasheet you provided. I agree most of things you wrote:

- pins 17 and 12 are FB-nodes that can be used for VOUT1 and VOUT2 adjustment, respectively
- MAX8538 CAN be used for DDR power supply i.e. provide supply voltage (VDD etc.) and required VREF/VTT
- MAX8538 CAN also be used for DDR power supply and Vcore generation and in that case the VREF/VTT-voltages are generated with another IC

--

If you are still playing with Vmodding , please post following info. Are your card looking like this (top view):

http://www.leadtek.com/3d_graphic/im...00_gttdh_2.jpg

.. if not do you know where to find a foto of the correct one ? In that top foto, could you locate any 'interesting' extra IC's ? Is it possible to 'track' with multimeter which components (bulk capacitors, inductors, MOSFET's) are connected to VOUT1 and VOUT2 of regulator.

You told to have some artefacts when altering one output of regulator (pin 17). Do you remember how high value you had when making that mod ?

Which output is controlling Vmem and how you performed that mod: value of resistor, corresponding voltage ..?

[Cybercat]

Thanks for the response, SikaRippa, and no it's not that one in the pic you linked to. It's this one:

http://www.newegg.com/Product/Produc...82E16814122207

I've been running a thread on the VR Zone forums, and I've made a lot more progress there on finding it, if you want to follow it.

http://www.vrforums.com/showthread.php?t=31684

Unfortunately the second card I've gotten is now dead as well, so progress has pretty much halted at that point. But maybe somebody out there with a 6800 PCIe (they all pretty much use the same PCB except the XFX model) will be willing to continue the process.

[SikaRippa]

Thanks for the response, SikaRippa, and no it's not that one in the pic you linked to. It's this one:

http://www.newegg.com/Product/Produc...82E16814122207

I've been running a thread on the VR Zone forums, and I've made a lot more progress there on finding it, if you want to follow it.

http://www.vrforums.com/showthread.php?t=31684

Unfortunately the second card I've gotten is now dead as well, so progress has pretty much halted at that point. But maybe somebody out there with a 6800 PCIe (they all pretty much use the same PCB except the XFX model) will be willing to continue the process.

OK.. Sorry about your card(s) Let's see whether I'll have time to check out the progress and if there are still anything to solve.

[Keks2K]

Hi guys !!! Here the information about vmem and vgpu mods of PX6800:


You need to connect 200K VR to TP15 and TP16 for VMEM mod, and 500K or 200K (500 is safer) VR to TP19 and TP17 for VGPU mod.
TPs (test points) are small metallized holes in the board.

vgpu mod helped me to get 500 mhz on 1.4v, mem mod didn't change anything

[Cybercat]

I don't believe it. Someone finally found the vmod. lol, too bad it doesn't do me a lot of good, but at least others will benefit. Thanks Keks2K!