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Very weird possible overclocking bug

post #1 of 8
Thread Starter 
Essentially, if I increase my memory OC by even 1Mhz I lose performance.

3DMark11 Graphics Test 4 P @ 1080p score with the core at 1200Mhz and vRAM at stock: 18.24-18.18fps
Same test with core at 1.2 and memory at 1245Mhz (5Mhz underclock): 18.22fps
Same test with core at 1.2 and memory at 1251mhz (1Mhz overclock): 17.69fps
Same test with core at 1.2 and memory at 1255Mhz (5Mhz overclock): 17.84fps

It stays around 17.8*fps until eventually crashing with coloured artifacts all over the screens I have plugged into the card, I'm thinking the GDDR5 on this card either barely passed QC or there's some software bug here at fault. TPU got 1775Mhz on the same model of card. I'm guessing I have Elpida chips (Not sure, not really wanting to take apart my PC to check) but I still should be able to get even a little further than stock on it at least, I'd hope.


Edit: Tested stock core, various memory clocks in OCCT and the highest I tested (1475Mhz) was fine...definite software issue.
Edited by Brutuz - 10/6/13 at 7:09pm
post #2 of 8
Might be a fabrication issue. Or maybe it's one of those GPUs that ''don't overclock well''.
Is your software updated? When did you last reinstall your operating system? You'd be amazed by the errors and crashed I get if I don't reinstall my OS....
post #3 of 8
Thread Starter 
I think it might have been the power saving features or something, I updated to 13.11 and disabled it and now can hit 1475Mhz easily.
post #4 of 8
Just asking ... did you increase the power limit?
Ayase Eli
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Ayase Eli
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Magicool 360 Ultra Magicool 240 Slim Dell U2713HM CM Storm MECH 
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post #5 of 8
Thread Starter 
Of course.
post #6 of 8
Answer is simple. Even GDDR5 memory has CAS latency. There are some frequencies where you have to set longer CAS/other latency (this can be done automatically). Once you cross it, performance of memory is decreased due prolonged access times, and gets better as you increase frequency further.

Other possible explanation is that memory is perfectly synced with other part of graphic card. In this situations memory can also provide better performance.
post #7 of 8
Quote:
Originally Posted by Offler View Post

Answer is simple. Even GDDR5 memory has CAS latency. There are some frequencies where you have to set longer CAS/other latency (this can be done automatically). Once you cross it, performance of memory is decreased due prolonged access times, and gets better as you increase frequency further.

Other possible explanation is that memory is perfectly synced with other part of graphic card. In this situations memory can also provide better performance.
Or simply ECC getting out of hand (GDDR5 has ECC)
Once too many errors occur ECC will spiral out of control and start having to take more time to correct errors
Ayase Eli
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Magicool 360 Ultra Magicool 240 Slim Dell U2713HM CM Storm MECH 
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Ayase Eli
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Zotac SSD Premium 480GB OCZ Vector 180 480GB Hitachi 7K3000 3TB 7200rpm Barrow 250mm Glass 
CoolingCoolingCoolingCooling
EK Supremacy MX EK-D5 X-TOP Rev.2 + Swiftech D5 Aquacomputer R9 290X "Bitspower EML" fittings 
CoolingCoolingMonitorKeyboard
Magicool 360 Ultra Magicool 240 Slim Dell U2713HM CM Storm MECH 
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post #8 of 8
Thread Starter 
Quote:
Originally Posted by Offler View Post

Answer is simple. Even GDDR5 memory has CAS latency. There are some frequencies where you have to set longer CAS/other latency (this can be done automatically). Once you cross it, performance of memory is decreased due prolonged access times, and gets better as you increase frequency further.

Other possible explanation is that memory is perfectly synced with other part of graphic card. In this situations memory can also provide better performance.

Reinstalling drivers, going to AB Beta 3.0 and just tweaking with settings fixed it, I think it was more a software bug in Afterburner or something.
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