Please post 7900GT / GTX overclock results

[Nilson]

So..

http://www.xtremesystems.org/forums/...&postcount=679
http://www.xtremesystems.org/forums/...&postcount=711
http://www.xtremesystems.org/forums/...&postcount=713
....where I'm talking about possible chip-memory/PCB issues....

My old posts about G71 over 700Mhz follow to the “freeze” issues: PC Perspective
Right after these news - many sites starts panic against GTX “freeze” issues. It was premature panic since now we have words from experienced peoples about the nature of these issues. After more detailed investigation of posts on different forums - I have conclusion:

1) First of all: NVIDIA says that some cards having isues when working on 700/1800 and higher- it's related to problems in communication between core and memory. I suppose it's due to different driving oscillator options for ROP, Geometry and memory.

2) The first words about pre-overcklocking from BFG, XFX, EVGA - the main reason - it's not true since many peoples says that even if they sets default clocks on these cards(pre-overclocked and with "freeze" issues) - it doesn't helps - the issue is still present. These cards have some defect element in their PCB - it can be bad chip or bad element on PCB(just try to remember issues with BlackScreen on 6800 cards - even on default clocks - it was releated to bad capacitors). These cards were RMA'ed and new cards were delivered to the owners - no issues on new cards.

3) The main number of posts with "freeze" issues were from EVGA owners. The root case was in bios since they were not able even to install default drivers from EVGA CD. Also, after new bios flashing some users still having problems with "freeze" issues - it's due to 2).

4) There are a few posts post in "freeze" threads about high temperature. Some GTX cards have bad or not correct installed cooler. Right after installing these cars from the box and playing games - the temp was more than 90C. RMA'ed - no issues now.

5) Some posts with "freeze" issus were solved via bios tuning. It was some kind of platform issues. (i.e decreasing RAM timings)

6) Some posts with "freeze" issues were related to overheat issues.

7) To avoid "freeze" issues - some time ago XFX and EVGA decrease their delta in the bios to +40. I suppose that first delta +50 was not correctly tested and it's hasty conclusion from Nvida.

8) The first reason of "freeze" issues due to OC - over OC: highly overclocked GPU - more than 720MHz is not stable due to clocks drops during high 3D load. It's all on default voltage for GTX and 1.55V for GT. It can be solved by increasing volts. Also, many 7900GT cards limited by 700-750MHz due to simple PCB and gpu limits.

9) The second reason of "freeze" issues due to OC - PCIe issues: proved that crads with more than 700-720 experienced problems with PCIe freq. I suppose it's due to synchro reasons between GPU driven clocks and PCIe. It can be solved by carefully PCIe tuning.

I suppose that new drivers - trying to restore 3D clocks after failure since if you check clocks after 3DMark run(with freezing in some subtests) - it will be 3D clocks. Also, if you check scores in bad subtests - you will see that scores in these subtests related to 2D or low-power 3D clocks.

So... If you have problems with "freeze" or PC shutdown during games on 650/1600 - forward this card to manufacture: it's real defect issue. If you have problems on clocks higher than 700MHz - check your temp and volts. In common case: 600-610MHz it's limit for 1.2V; 690-700MHz it's limit for 1.4V; 720-750MHz it's limit for 1.55V. If you volts and temp are correct - check you PCIe freq. In common case: you need to increase PCIe freq: it should be done carefully -> +1MHz PCIe freq then try to find stable OC for your card -> then repeat it: +1MHz PCIe freq and so on...

Hope this helps you to understand and determine your problems.

ps: sorry for my bad engl ..."from Russia with love" (c)....