It's time to do some actual testing with these cards. We'll start off by showing you some tests we have done on overall power consumption of the PC. Looking at it from a performance versus wattage point of view, the power consumption is really good with the new 55nm products. Our single card test system is a Core 2 Duo E8400 (3GHz) Processor, the nForce 680i SLI mainboard, a passive water-cooling solution on the CPU, 2GB memory, DVD-ROM and WD Raptor drive. Have a look:

A single Radeon HD 4850/4870 series requires you to have a 500 Watt power supply unit at minimum if you use it in a high-end system, and I think that's barely on the safe side. Also recommended is 32 AMP's on the 12 volts rails for stable power distribution (in a single card configuration). Please make note of the fact that the card uses two 6-pin power connectors.

Crossfire is something else, you add another 130-150 Watts plus 8 AMPs on the 12V rails during gaming. I recommend a PSU of, at the very least, 750-800 Watts. Make sure you have some reserves folks. It's not that your PC will consume that much power, it's just that you want to make sure your PSU can deal with the hefty load and will stay stable during you entire gaming experience.

With three cards obviously 800+ Watt power supplies are recommended, and in fact even needed to be able to even supply something as simple as enough PCIe graphics power connectors.

There are many good PSU's available, over the years we reviewed a lot of them and have loads of recommended PSU's for you to check out in there, have a look. Things that can happen if your PSU can't cope with the load?:

• bad 3D performance
• crashing games
• spontaneous reset or imminent shutdown of the PC
• freezes during gameplay
• PSU overload can cause it to break down

The thermal envelope

PowerColor Radeon HD 4850 thermals
We measured at a room temperature of 21-22 Degrees C, look at idle temperature and then load the GPU 100% for a couple of minutes and measure the temperature once a second and follow the temperature delta.

Typically the standard Radeon 4850 products come with a bit of an average cooler. Temperatures can rise up-to 95 Degrees C on these products. So I was quite thrilled to see a much better cooling solution mounted to this product.

Idle temps are roughly 45 Degrees C, yet when the GPU is fully utilized we measured 68 Degrees C, which is much better than the reference cooler.

Always make sure you have a very well ventilated PC, as that heat is dumped inside your PC due to the single slot cooling design. This is definitely one of the negatives of the product.

Noise Levels coming from the graphics card

When graphics cards produce a lot of heat, that heat usually needs to be transported away from the hot core as fast as possible. Often you'll see massive active fan solutions that can indeed get rid of the heat, yet all the fans these days make the PC a noisy son of a gun. I'm doing a little try-out today with noise monitoring, so basically the test we do is extremely subjective. We bought a certified dBA meter and will start measuring how many dBA originate from the PC. Why is this subjective, you ask? Well, there is always noise in the background, from the streets, from the HD, PSU fan etc etc, so this is by a mile or two not a precise measurement. You could only achieve objective measurement in a sound test chamber.

The human hearing system has different sensitivities at different frequencies. This means that the perception of noise is not at all equal at every frequency. Noise with significant measured levels (in dB) at high or low frequencies will not be as annoying as it would be when its energy is concentrated in the middle frequencies. In other words, the measured noise levels in dB will not reflect the actual human perception of the loudness of the noise. That's why we measure the dBa level. A specific circuit is added to the sound level meter to correct its reading in regard to this concept. This reading is the noise level in dBA. The letter A is added to indicate the correction that was made in the measurement. Frequencies below 1kHz and above 6kHz are attenuated, where as frequencies between 1kHz and 6kHz are amplified by the A weighting. 

We start up a benchmark and leave it running for a while. The fan rotational speed remains constant. We take the dBA meter, move away 75 CM and then aim the device at the active fan on the graphics card.

The ZeroTHREM cooler isn't that noisy either. Expect roughly 40 dBa when the GPU is fully stressed. In idle you can hardly hear the cooler though, so noise wise this is a great product.