Extreme Overclocking of MSI NBOX (NVIDIA GeForce FX 5900 Ultra)

GPU Overclocking

The maximum frequency the NVIDIA GeForce FX 5900 Ultra chip on MSI’s card could handle during extreme overclocking was 675MHz. This seemed an outstanding achievement and a new record!

However, I was not joyous for long. Having tested MSI card at different graphics chip frequencies, I got very curious results. Below you can see the graph showing the relation between the graphics core frequency and the card’s performance at a fixed memory frequency:

As you see, when the GPU clock-rate grew above 625MHz, the card ran more slowly than at its regular frequencies. Moreover, the results don’t change at higher graphics chip frequencies.

It is known that NVIDIA GeForce FX 5900 / 5900 Ultra chips have integrated thermal diodes. It seems like the temperature of the GPU is too high at frequencies above 625MHz (in spite of our water-cooling solution) and, following the instinct of self-preservation, the driver drops the frequencies of the card even below the standard 3D mode ones. This is also evident from the GPU voltage value. It should be 1.4V plus my addition, while at frequencies above 625MHz it is actually 1.2V + my addition.

In some cases, the graphics card was going through the test at the overclocked core frequency, but then would hang up for a moment, lower the GPU voltage and drop down to lower working frequencies. It continued through the rest of the test then, but certainly with unsatisfactory results.

Thus, although the card proved to be operational at 675MHz GPU frequency, it did best at 625MHz graphics chip working frequency. This frequency will be considered the maximum GPU overclocking result.

Now, let’s estimate the gains we achieve by overclocking NVIDIA GeForce FX 5900 Ultra in various work modes. I drew a graph showing the performance increase from overclocking as compared to normal frequencies. I also put down the gain of the GPU frequency.

As we have expected, the graphics core overclocking is most advantageous in the modes that use anisotropic filtering. GeForce FX 5900 Ultra spends many clock cycles of its pixel pipelines to perform AF and a higher GPU frequency gives it a boost.

When full-screen anti-aliasing is enabled, we have a smaller gain. FSAA dramatically increases the memory bus workload, but we have kept the memory frequency intact here.

Overall, the performance gain was twice lower than the GPU frequency gain even in the most “responsive” mode, about 20% at maximum. So, overclocking the GPU only makes no sense: let’s speed up the memory.