X-bit labs

NVIDIA GeForce FX 5900 XT FAQ: All You Need to Know About It (page 7)

Category: Video

by Kirill "ALT-F13" Balalin

[ 05/05/2004 | 04:29 PM ]

3.4.  Why does my desperately overclocked 5900XT work slower than before overclocking?

3.4.1.  What is “auto-brake”?

NVIDIA implements special security measures in its driver. They show themselves in the card’s reducing the GPU frequency to 376MHz with the ensuing performance hit. This often happens during a test, thus resulting in a low score (even lower than at the regular frequencies). This “auto-brake” is the main obstacle to overclocking a 5900XT graphics card. It may show differently (personally, I saw this effect only twice – the card either works at the high frequencies with the maximum speed or hangs up) and doesn’t greatly depend on the testing conditions (temperature, voltages). Interesting fact – on Detonator 44.03 auto-brake works much more severe, than on 53.03 and other 5x.xx series drivers, which leads to massive (up to 50MHz) maximum core overclocking drop.

3.4.2.  Why are the frequencies dropped down?

Says Unwinder, the author of RivaTuner, “The driver protects against over-overclocking. If the internal stress test fails or if some critical temperature threshold is reached, the card switches back to 2D and you cannot return it into 3D without rebooting. If you have any doubts about the test results – check out the real frequencies with the monitoring module of RivaTuner”.

3.4.3.  What’s wrong with thermal monitoring?

It has been observed that graphics cards with enabled thermal monitoring use the auto-brake more actively.

3.4.4.  How do you deal with the auto-brake?

You have three options, depending on what your needs are:

• Don’t overclock to the limit. You can usually find a threshold after which there’s a higher chance of the auto-brake to snap into operation (although the card is stable and doesn’t heat up). Don’t exceed this threshold.
• Flash the BIOS from the ASUS V9950SE – it may help (see Item 3.5.5);
• If you needn’t get rid of the auto-brake completely, but want to avoid it without rebooting (this is especially necessary for testers) – read the recipe from LaikrodiZ. 

3.4.5.  How do you roll the frequencies back after the auto-brake without reboot?

Unwinder was wrong – you can roll the card back into 3D frequencies without rebooting the system. And you need his program for that! The method follows:

• Unlock 3D frequencies in the Overclocking tab. The memory will be all right, while the chip will plunge down to 300 or 376MHz;
• Now unlock 2D frequencies and set up the desired 3D frequency instead of the normal 300MHz;
• Without clicking Test or Apply (that is, without actually changing the frequency), you switch back to the 3D clock rates controls. When switching between the tabs, the frequency of the chip will return to the normal value (which you have previously set up in the 2D frequencies tab);
• From this moment on, you can control the 3D frequency in the usual way. On another auto-brake, repeat the operation once again.
• I really wonder how LaikrodiZ found this combination out?!