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Can't overclock 6950CF as high after changing heatsinks (temps lower)?

February 22, 2013 1:41:17 AM

My system:
OS: Windows 7 64 bit
Case: Antec Twelve Hundred V3 Black Steel ATI Full Tower
Motherboard: ASUS M4A89TD PRO/USB3
CPU: AMD Phenom II X4 965 Black Edition at 4.0GHz
CPU Heatsink: ZALMAN CNPS9900MAX-B
GPU: XFX Raedon HD 6950 2GB Crossfire
GPU Heatsinks: Accelero Xtreme III
RAM: G.SKILL Ripjaws X Series 16GB DDR3 1600 7-8-7-24-37-2T
PSU: Rosewill BRONZE Series RBR1000-M 1000W
HDD: Seagate 500 GB SATA III 7200 rpm
SSD: OCZ Vertex 3 128 GB SATA III


So I just got a pair of Accelero Xtreme III coolers for my XFX 6950 2GB CF setup because I was having trouble with temps while under load.

It's been frigid here, so I was able to run the CF setup at 950-960 core, 1.225V, +20% Power, 1250 memory with the window next to my computer open a bit to help keep the temperatures down. At times the stock fans were getting close to 90C at 100% fan and I was experiencing some stability issues, with idle temps being around 50-60C.

I bought the pair of coolers and installed them and now I'm idling around 30-32 and never really hitting 60C at load. All of the temperatures in GPU-Z (including #1-3 and VRM) have gone down tremendously, however, I'm now struggling to overclock at the same speeds that I was before without artifacting/display drivers crashing.

I can get up to 900 core at stock (1.1V) voltages, but when I try hitting the 950 or 960 that I was getting previously, no matter what voltage I try, I immediately get white/magenta pixels and small artifacts and eventually have to go into the Task Manager to end the benchmark/game's process. I haven't had any outright crashes or BSODs.

Anyone have any ideas of what the problem could be? I haven't changed anything except that I spent a few hours taking out the cards and drive bays in my Antec 1200 to clean out the dust and then replaced the HSFs on the GPUs and put them back in. I also changed around some of the cable management in order to fit the coolers because they were much longer than my cards were originally with the stock coolers.
!