Power Consumption & Temperatures
Relatively speaking, both the Radeon HD 4890 and GeForce GTX 275 use very little power with just 3 watts separating them under full load. The Radeon HD 4890 was slightly more power hungry at idle, using 16 watts more when compared to the GeForce GTX 275.
We tested both cards using their standard reference coolers and as such these results will reflect those of any Radeon HD 4890 or GeForce GTX 275 using the stock cooler designed by ATI and Nvidia, respectively (about 80% of the products on offer).
The Radeon HD 4890 is a noisy little thing under load, though the screaming blower fan manages to keep the GPU relatively cool at just 69 degrees. Then at idle the fan almost turns off, so the GPU doesn't drop below 50 degrees.
The GeForce GTX 275 reaches a toasty 78 degrees under load, but will cool down to 41 degrees at idle. The fan on the GeForce is more moderate, making more noise than the Radeon at idle but remaining quieter under full load. Neither card is of the silent type, though the Radeon was considerably noisier when running 3d applications.