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. We tested all of the video cards using the Asus P5N32-SLI SE Deluxe motherboard, save for the CrossFire system, which required a different chipset. For that system, we used an Intel D975XBX motherboard.

The idle measurements were taken at the Windows desktop. The cards were tested under load running Oblivion using the game's Ultra Quality setting at 1600x1200 resolution with 16X anisotropic filtering.

The performance race between the Radeon X1650 XT and the GeForce 7600 GT is practically too close to call, but here we see some real differences. The X1650 XT draws about 10W more than the 7600 GT at idle and about 30W more under load. That's really not surprising considering that the Nvidia G73 GPU is about 125 mm², while the RV570 is 230 mm². Oddly enough, the X1650 XT seems to draw a little more power than the higher end Radeon X1950 Pro based on the same GPU.

Noise levels and cooling
We measured noise levels on our test systems, sitting on an open test bench, using an Extech model 407727 digital sound level meter. The meter was mounted on a tripod approximately 14" from the test system at a height even with the top of the video card. The meter was aimed at the very center of the test systems' motherboards, so that no airflow from the CPU or video card coolers passed directly over the meter's microphone. 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, including CPU and chipset fans. We had temperature-based fan speed controls enabled on the motherboard, just as we would in a working system. We think that's a fair method of measuring, since (to give one example) running a pair of cards in SLI may cause the motherboard's coolers to work harder. The motherboard we used for all single-card and SLI configurations was the Asus P5N32-SLI SE Deluxe, which on our open test bench required an auxiliary chipset cooler. The Asus P5W DH Deluxe motherboard we used for CrossFire testing didn't require a chipset cooler, so those systems were inherently a little bit quieter. In all cases, we used a Zalman CNPS9500 LED to cool the CPU.

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.

We measured the coolers at idle on the Windows desktop and under load while playing back our Quake 4 nettimedemo. The cards were given plenty of opportunity to heat up while playing back the demo multiple times. Still, in some cases, the coolers did not ramp up to their very highest speeds under load. The Radeon X1800 GTO and Radeon X1900 cards, for instance, could have been louder had they needed to crank up their blowers to top speed. Fortunately, that wasn't necessary in this case, even after running a game for an extended period of time.

You'll see two sets of numbers for the GeForce 7950 GT below, one for the XFX cards with their passive cooling and another for the BFG Tech cards, which use the stock Nvidia active cooler. I measured them both for an obvious reason: they were going to produce very different results.

As we've noted before, small coolers tend to be noisy, and the X1650 XT can't entirely escape that fact. This card really isn't a terrible offender overall. It's a little louder at idle than most, but not horrible. While running a game, the X1650 XT's cooler doesn't crank up to the kind of high-pitched whine you get from the GeForce 7600 GT, thank goodness. The difference shows on our decibel meter.

CrossFire, on the other hand, is another story—especially under load. I'm not sure if there was some kind of odd harmonic effect between the two X1650 cards' coolers or what. Readings on the decibel meter seemed to cycle up and down through a much broader range than we've seen from other coolers. I tried to pick a reasonable center of that range to include in our results, and it turned out to be louder than anything else we've recorded. I wouldn't worry too much about that, though. Subjectively, the X1650 XT isn't an especially loud card.

Overclocking
I had some trouble using ATI's auto-overclocking utility to find the optimal clock speed in our Radeon X1950 Pro review, but I ran into no such issues with the X1650 XT. The utility settled on 621MHz core and 763MHz memory clocks for both single-card and CrossFire configs—pretty much maxing out the peak values for the manual sliders in the control panel—and both were stable at those speeds.

Unfortunately, overclocking this thing to the apparent max in ATI's control panel doesn't get you much additional performance. The headroom does seem to be there, though, to take it up quite a ways.