Sapphire x1950 pro rev2 voltmod overclock

OK, first some introductory info.

I have a sapphire x1950 pro (newer revision, with fan on bracket end)


I upgraded the cooling with a Thermalright HR-03 heatsink with 2x80cm Arctic cooling 8 PWM fans. The brass thing holding it on is a "Zenith Plate Hanger for 14-20cm plates" that I got from Bunnings. The two fans are held together by the "angle drive" that comes with the plate hanger which is nailed to the wall when you actually use it to hang plates! I just wrapped it around the fan bases and crimped it so the fans don't slide sideways (the wire supports that came with the heatsink are for a single, standard "open" 92cm fan. so I couldn't use those. I also used some eye hooks that screwed into some conviently located and sized holes in the heatsink! These fans are near silent at 100%, silent at around 70-80%. This setup keeps my card below 40C no matter what I throw at it! (it's winter here so ambient is 10-20C.


This is what I used for the voltmods:


Initial measurements:
VGPU: 1.26V
OGPU: 6440 ohms
I also checked resistances and continuity of surrounding resistors to make sure they weren't getting changed or shorted, which I would definately recommend doing for your own sanity when things go wrong!

Here are various readings I took after pencil mods (OGPU/VGPU)
5710/1.408
5610/1.45
5260/1.445
5770/1.435
I know they are a bit wierd but I swear they are more or less accurate. Keep in mind resistance/voltage will go up and down a bit after turn on - my guess is the current smooths out the pencil a bit. What I worked out in the end was stability drops off around 1.4 volts (after turn on and warm up) which correlates to around about 5800ohm (measured before turn on.)

I have it stable now at 5840/1.391 with GPU at 702Mhz (default 580, 21% oc.) Highest I have completed a 3dmark05 is 722 - but it crashed soon after.

Also what I found was if the frequency is too high GPU recover will generally save it (unless you really go hard), but if the voltage is too high it will black screen.

Some tips:
Nice sharp pencil (i used a HB)
Applying pencil is very inaccurate - go past where you want then
-Blow moderately just near the PCB
-remeasure, repeat

Next I'll start on the memory, and maybe push the gpu a little more once the new resistance is a bit more stable.

Thanks to Wiz, Mad Cow, and everyone who posted stuff to help me!

Memory voltmod has undesireable effect

Initial reading:
Vmem = 1.721
After mod:
Vmem = 1.905

Previous max mem frequency before artifacts was 783. After the voltmod it seems to be 756 - so I guess either this is the wrong voltage being changed, or extra voltage makes it worse.

Any ideas?

sweet! is yours a sapphire too? stock cooling? what temps are you getting? my voltage maxxed out around 1.45... but its unstable at anything over 1.41. Keep in mind the voltage will keep going up for a week or two after the mod - I've had to increase my resistance a couple of times already to keep it from crashing. also, i have heatsinks now on the chips and transistors on the power connector end because they were getting really hot. (see other forums about vrm cooling.)

I've settled on 702gpu/756mem now - voltmodding the memory doesn't help at all for me, maybe you will have better results. btw - you need to increase memory at 27mhz increments or it will crash.

nope, agp/pci-x voltage (from your bios) is something else. I don't know what it does to be honest, probably used on cheap cards that don't have their own voltage regulation or is part of the communication from graphics card to motherboard.

vgpu is managed by the videocard itself. it is the voltage supplied to the graphics chip. some cards let you change it with bios/software, but these sapphire cards don't. the only way you can change it is to modify a component on the card itself - see my first post. you must change a resistance value that controls the voltage. there is no monitor for gpu voltage, you have to measure it by hand with a multimeter. increasing the agp/pci-x voltage in your motherboards bios won't help, and it might actually hinder overclocking. so leave it at default.

lillebror - yep thats similar to me. it does seem to drop 0.2v for some reason that goes back up again later. maybe this is actually on purpose by the card, like a powersaving mode or something?
widjaja - the cooling is effective but it takes up 4 vacant slots! thats ok though coz i don't have any other cards.