never OC graphic's card before, but wanting to have a shoot at it, any good tips, as i don't want to blow either 1 up,
i have 2 x 1gb asus 6950's setup in crossfire, have msi afterburner, can run crysis 2 at max settings, but want to try MW3 and BF3
i'm using 2 x bridges,
been reading on net, some say 1 and some say 2, but all depends on what you using it for....
Some people say that two bridges can hurt performance, but then other sites say that two bridges help balance out the information flow.
So should I use one or two?
my spec's are
Coolermaster Sniper scout case.
Corsair HX850W PSU.
AMD phenom ii x4 965 BE.
Corsair hydro H60
(with extra fan for push pull configuration)
ASUS M4A77TD_PRO MB.
16gb 1333mhz DDR3, with Arctic Cooling.
2 x ASUS HD6950 in CrossfireX
Western Digital VelociRaptor 300GB OS.
these are my heaven results
Heaven Benchmark v2.5 Basic
Windows 32bit Visual C++ 1600 Release Mar 1 2011
Windows 7 (build 7601, Service Pack 1) 64bit
AMD Phenom(tm) II X4 965 Processor
3415MHz MMX+ 3DNow!+ SSE SSE2 SSE3 SSE4A HTT
AMD Radeon HD 6900 Series 8.911.0.0 CrossFireX 1024Mb
As far as CFX bridges go, it's a good idea to try 1 and 2 respectively. I found I got bad performance using 2 bridges when I first installed my cards so I've been running a single bridge for a long time now. The only reason there's 2 bridge slots as far as I know, is to "daisy chain" bridges so you can do 3 way and 4 way CFX. I might be wrong, though.
As for overclocking, here is my suggestions based on experience:
1) Use whatever program you want for OCing. I like MSI Afterburner. You also may need to go to the Afterburner config file and change "allow unofficial overclock" to "1".
2) Begin with increasing memory speed by 25mhz, and testing using Furmark with 4xMSAA at max resolution and full screen. Watch that your temps don't get crazy. If they go over 80C, I suggest you go into Afterburner and make a custom fan profile. I also suggest you run GPUZ in the background to check all your temp sensors, since VRM and VRAM might increase a lot more than the core temp.
3) Allow the card to get to an equilibrium temp (~5-10 mins) and give it 2-3 mins at this temp. For future testing try to make the changes quick to keep the temps up as that is something that is going to be a big factor in stability later on.
4) If successful, increase memory by another 25mhz and do it again, until it's unstable. You will either get artifacting or a crash/BSOD. I'd also suggest you check online to see what other people are running just to have an idea.
5) If it crashes, lower it by 25mhz or less and basically try to get it dialed in as best as you can.
6) Begin the same process with Core speed, but run it at 0xMSAA. Once you find an unstable core speed, if you want you can increase the voltage (if that is available to you) by 0.05V or so. I do not really recommend doing this except for benchmarking. IMO, get as much as you can out of it at stock volts.
7) If you think you found your max core and memory speeds, run some benchmarks. As it happens, you can start to lose performance from having too high memory speed - basically instead of outright crashing it will slow down by having to "resend" data packets that fail. Simply dropping 5-10mhz off the memory can have a dramatic improvement.
8) Once you've done that, start gaming! If there's any crashing, you'll want to tweak a little more by lowering 5mhz on memory first. If it doesn't fix it, lower core by 5. Repeat until stable.