Non reference XFX 7900GS help please

[Sam__]

I started to look for a vmod for this well over a year ago and gave up as I couldnt find any info on this non-reference PCB.

Heres a pic:

http://i195.photobucket.com/albums/z25/sam__07/Comp/IM000151Medium.jpg

So today, after gaining confidence with hard vmodding an 8400GS, I decided to have another go with this thing.

The one thing that got me is thers only one chip on the back and it only has one feedabck pin. Data sheet here (http://pdf1.alldatasheet.com/datasheet-pdf/view/205424/SEMTECH/SC2621STRT.html) So im not sure what this controls. Is ther any other way of finding out other than just running a VR to ground and measuring which one, vgpu or vmem, changes?

Also I can only find one inductor from which to measure voltage. I get 2v and 1.5v from the legs, so i presume this is for the vmem. Is there anything else I can look for to measure the vgpu?

I can get more pics if it will help people.

[Sam__]

anyone? :(

[ceemic]

Can You do better macro pictures from these ICs?
http://ceemic.pri.ee/hardware/xfx7900gs.jpg
And what is the little thing there?

Also, do an overview shot from the front of the card. Often some controllers are there, not in back...

[K404]

What ceemic said really. High-res pics and we should be able to help :)

XFX PCBs arent the best to work with, but maybe because its non-ref it will be more reliable. I got through 5 of the ref design last year between the GS, GT and 7950GT.

[Sam__]

Hope these help, sorry the camera is a pos but its the only one i got atm. Ill write down the chip names cos i doubt it picked em up.

Top chip is: 4405 B06Z18 I think. Its not very clear.
Bottom one is linked to in first post : SC2621S
http://i195.photobucket.com/albums/z25/sam__07/Comp/IM000157Medium.jpg


LEft chip is : 73ANY6K G4 ACT08
Right is : MEC25LV512 E0650 080359C
http://i195.photobucket.com/albums/z25/sam__07/Comp/IM000167Medium.jpg


Chip in the middle is : AT-8A Q0H
http://i195.photobucket.com/albums/z25/sam__07/Comp/IM000161Medium.jpg

That any help?

[K404]

SC2621S I think will be the VGDDR supply. FB pin is #5. GND is #9. Trimmer value will be 20x the resistance between those 2 pins.

datasheet: http://www.alldatasheet.com/view.jsp?Searchword=SC2621S



I think AT-8A Q0H will be for VCore but I can never find the datasheets for those kind of ICs....They're so small you'll probs need to probe all the SMC around it for the right mod point and a better soldering point

[Sam__]

SC2621S I think will be the VGDDR supply. FB pin is #5. GND is #9. Trimmer value will be 20x the resistance between those 2 pins.

datasheet: http://www.alldatasheet.com/view.jsp?Searchword=SC2621S

Well at least i know i got that bit right. :D.

I think AT-8A Q0H will be for VCore but I can never find the datasheets for those kind of ICs....They're so small you'll probs need to probe all the SMC around it for the right mod point and a better soldering point

kwl, thanks. I'll have a look around for it, see i fi can get any info.

[Sam__]

I havnt foud the pin diagram for the other chip yet but Iv done some MM testing. Pin8 has a resistance of 784 to ground. which seems the most logical for the feedback pin. Any others that read resistance gave like 10-20K. I'll test again in the morn cos im a bit tired now so not so steady with the probes.

Also found two solder points that were connected to pin8. shown in green.

http://i195.photobucket.com/albums/z25/sam__07/Comp/IM000161Medium2.jpg

[ceemic]

Sam__, FB is connected to GND throught resistor(s) and it's connected with Vgpu through another resistor ;)

[Sam__]

Sam__, FB is connected to GND throught resistor(s) and it's connected with Vgpu through another resistor ;)

are you saying thats the right chip? or i might not have the right pin?

[ceemic]

Sam__, it can be the right chip and even right pin.
Use 20k VR and and You'll see if Vgpu changes...

[Sam__]

Sam__, it can be the right chip and even right pin.
Use 20k VR and and You'll see if Vgpu changes...

ah kwl, the only problem is i dont have a measure point for the vgpu :(.

[Sam__]

I spose i could just use v(new) = v(stock) x [ r(stock) / r(new) ] but it would e nice to have confirmation of the voltage.

Are there any other components that would give the vgpu other than inductors. Heres a pic of the front. sorry its a rubbish pic, but you get the idea.

http://i195.photobucket.com/albums/z25/sam__07/Comp/IM000166Medium.jpg

[K404]

Theres a space for a capacitor thats not populated. Try those points, might work

OR.... seeing as the caps look to be mainly surface mounted, probe the spare contact area.

Just probe everywhere with a DMM until you get something that looks right. It should change under 3D load, so that will be the giveaway. The more you probe, the faster you'll find points because you'll see the patterns emerge ;)

Its not meant to be flippant...id rather give guys a fishing rod than a fish :)

[Sam__]

Theres a space for a capacitor thats not populated. Try those points, might work

OR.... seeing as the caps look to be mainly surface mounted, probe the spare contact area.

Just probe everywhere with a DMM until you get something that looks right. It should change under 3D load, so that will be the giveaway. The more you probe, the faster you'll find points because you'll see the patterns emerge ;)

Its not meant to be flippant...id rather give guys a fishing rod than a fish :)

and id rather learn to fish than be given a ham.....oh no, ah thatl do. :D

Sounds like id better get poking :D. I'll report back when/if i find anything.

[Sam__]

Think I found my points!! What you think? (both points read the same)

http://i195.photobucket.com/albums/z25/sam__07/Comp/IM000151Mediumv.jpg

[Sam__]

I can confirm that the Vmods work, will get pics up in a bit and hopefully have a play with it 2moz. thanka a lot guys.

heres some durin pics:

http://i195.photobucket.com/albums/z25/sam__07/Comp/IM000170Medium.jpg

http://i195.photobucket.com/albums/z25/sam__07/Comp/IM000175Medium.jpg

Just need to put the read points on.

[i found nemo]

sam

i love ur heatsink!!!

[Sam__]

sam

i love ur heatsink!!!

lol, thanks. its an old AMD heatsink ziptied on.

[Sam__]

Finished pics:

http://i195.photobucket.com/albums/z25/sam__07/Comp/IM000181Medium.jpg

http://i195.photobucket.com/albums/z25/sam__07/Comp/IM000179Medium.jpg

[ceemic]

Nice to see, it worked out for You!
Good luck :up:

[Sam__]

got the core to 720 with 1.6v and the mem to 900 with 2.12v so far, need more time to get more out of it, i know i can.