Overclocking Extravaganza: GTX 275's Complex Characteristics

After our in depth look at overclocking with AMD's Radeon HD 4890, many of our readers wanted to see the same thing done with NVIDIA's GTX 275. We had planned on looking at both parts from the beginning, but we knew each review would take a bit of time and effort to design and put together. Our goal has been to try and design tests that would best show the particular overclocking characteristics of the different hardware, and shoehorning all that into one review would be difficult. Different approaches are needed to evaluate overclocking with AMD and NVIDIA hardware.

For our AMD tests, we only needed to worry about memory and core clock speed. This gave us some freedom to look at clock scaling in order to better understand the hardware. On the other hand, NVIDIA divides their GPU up a bit more and has another, higher speed, clock domain for shader hardware. Throwing another variable in there has a multiplicative impact on our testing, and we had a hard time deciding what tests really mattered. If we had simply used the same approach we did with the 4890 article, we would have ended up with way too much data to easily present or meaningfully analyze.

We've kept a few key test points, as we will look at each clock at the highest speed we could achieve on its own (all other clocks set at stock speeds). We will also look at performance with all clocks set to the maximum we could hit. Beyond this, rather than looking at how performance scales over clock speed with memory and shader at their maximum and looking at how performance scales over shader speed with memory and core at their maximum, we decided it would be cleaner to look at just one more configuration. For this test, we chose core and shader speed at maximum with memory at stock.

As with the previous look at overclocking, we present our analysis based on percent increases in performance but provide the raw data as well. It's all pretty straight forward with the raw data, and we do include our highly overclocked 4890 as well as the 900MHz core clocked 4890 that can be picked up pre-overclocked from the manufacturer. For the bulk of the article, we will just be considering the impact of overclocking on the GTX 275, but our conclusion will compare AMD and NVIDIA on overclocking in this segment.

The clock speeds we were able to pull out of our GTX 275 were not to shabby as far as overclocks go. Our core clock speed could have been better, but otherwise we did pretty well. Here is what we will be looking at today:

Core: 702MHz (vs. 633MHz stock)
Memory: 1296MHz (vs. 1134MHz stock)
Shader: 1656MHz (vs. 1404MHz stock)

These are 10.9, 14.3, and 17.9 percent increases respectively. First up, we'll look at the impact of overclocking the memory, then we'll move on to core and shader. After that it's on to fully overclocked and our core/shader combined overclock.