Help needed with 3870 OC

[sam0t]

Hello,

I have hitted a dead end with my CLUB 3D 3870 OC venture and could use advice. The card does not seem to be able to OC one bit. Even a mild OC from the default core 777MHz > 800MHz is enought to crash my card. Memory on the other hand has not problems runnin over 1200MHz speeds (no artifacts and such).

I have overclocked with CCC overdrive and latest Rivaturner, with both the card crashes. So I turned to tweaking BIOS, and used RBE to mod the latest Sapphire 3870 .77 BIOS a bit. Here is a screenshot of my latest BIOS flash file:

http://img399.imageshack.us/img399/600/rbeui9.jpg

As you can see, I have bumped up the 3D voltage fair bit with no help. Is there a way to check the over volting through BIOS really works?

[sneekypeet]

you could use a DMM to read the voltages on the card with something like furbench running to load the GPU.

Look into RM's thread and see if you have the correct points to read voltages here...http://forums.techpowerup.com/showthread.php?t=48544

If not he still may be able to help you find the read points!

[sam0t]

Thanks for the tip, I shall read through that thread.

Mostly Iam curious about 3870 core voltage limit, which is the safe number of volts a 3870 core can take without breaking. Iam assuming 1.4v is not critical yet ?

edit:

I give up, it seems my 3870 is destined not to break the GPU core 800MHz line. I upped the core voltage to 1.4 with RBE and tried with another BIOS version, but still the card crashes with core 800MHz speed. 790MHz core is perfectly stable even if the temps (load ~80c) are similiar to that of 800MHz core speed. Looks like I have an unfortunate individual. My card is from the first batch of the cards, maybe thats the reason :/ ?

[sam0t]

Ok so it seems that the RBE is the real culprit behind my crashing. I tested this by changing my cards default bios just slightly (fan speed) and flashed the card. I get instant crash after 1 minute of furmark. So I flashed back my unchanged BIOS and it works flawlessly. Note that this is with same core/mem speeds , I only changed the fan speed by 1% .. O_o

ps. Weird notification, whenever I use RBE modded BIOS, my card reports to be running 10c cooler on load than with non edited BIOS. This is with the same fan speeds. :/

Looks like I have to use the pencil volt mod as softmodding does not work for my card.

edit:

Just to let people know, after flashing .71 ATI made bios from TPU VGA collection I have been able to OC the card succesfully to 830/1250 speeds with CCC Overdrive. This is one of those WTF cases again, it would be intresting to know why RBE modded BIOS files fail totally with this card, perhaps a bug in RBE ? :/