Power consumption
We measured total system power consumption at the wall socket using an Extech power analyzer model 380803. The monitor was plugged into a separate outlet, so its power draw was not part of our measurement. The cards were plugged into a motherboard on an open test bench.

The idle measurements were taken at the Windows Vista desktop with the Aero theme enabled. The cards were tested under load running Left 4 Dead at 2560x1600 resolution.

True to form for a small, 40nm GPU, the Radeon HD 4770 draws less power than any other graphics card we measured under load. When idle at the Windows desktop, it draws more power than a couple of GeForce cards, though not the 9800 GT. Nvidia has made some nice strides in idle power use with its newer designs, but the older 9800 GT (which is just a renamed GeForce 8800 GT) doesn't benefit from that work.

Noise levels
We measured noise levels on our test system, sitting on an open test bench, using an Extech model 407738 digital sound level meter. The meter was mounted on a tripod approximately 8" from the test system at a height even with the top of the video card. We used the OSHA-standard weighting and speed for these measurements.

You can think of these noise level measurements much like our system power consumption tests, because the entire systems' noise levels were measured. Of course, noise levels will vary greatly in the real world along with the acoustic properties of the PC enclosure used, whether the enclosure provides adequate cooling to avoid a card's highest fan speeds, placement of the enclosure in the room, and a whole range of other variables. These results should give a reasonably good picture of comparative fan noise, though.

I've tested the stock-AMD and Asus versions of the Radeon HD 4770 here, since they have different coolers. As you might expect from looking at the power consumption numbers, though, neither has to be very loud to keep the RV740 GPU cool. Surprisingly, the Asus 9800 GT Matrix is the noisiest card we tested under load. The Matrix cooler has aggressive fan speed settings and is made for overclocking. I know for a fact we've tested much quieter GeForce 9800 GTs in the past.

Speaking of noisy coolers, you should hear how the reference 4770 card sounds at power-on, when it briefly cranks up to full speed. The thing has a medium-pitched whine/roar, evoking the infamous Dustbuster on the GeForce FX 5800 Ultra, not the silky-smooth hiss of, say, a Radeon HD 4870 reference cooler. Obviously, the 4770 cooler had no need to reach top speed when we tested noise levels, but I found that it did briefly step to a higher gear from time to time as I used it in other games. To give you some idea how this cooler's peak speed compares to its usual noise levels, I manually set its speed to 100% and measured a noise level of 63 dB. By contrast, the Asus card's cooler topped out at just 58.4 dB, worlds apart to my ears.

GPU temperatures
I used GPU-Z to log temperatures during our load testing. In the case of multi-GPU setups, I recorded temperatures on the primary card.

The 4770 matches the 9800 GT at a relatively cool 65°C. That's a far cry—well, 20°, really—from the temperatures we've observed under load with a stock Radeon HD 4850. Among the cards tested, only two Asus Radeon HD 4800-series cards maintain lower temperatures, although those same coolers essentially fail in CrossFire mode, as the numbers above reflect. (They were recorded just before the system locked up.)