We'd like to cover a few final data points before bringing this article to a close. Throughout all of our benchmarking and testing, we monitored how much power our test systems were consuming using a power meter. Our goal was to give you an idea as to how much power each configuration used while idling and under a heavy workload. Please keep in mind that we were testing total system power consumption at the outlet here, not just the power being drawn by the motherboards alone.
Although AMD claimed the Radeon HD 4890 would consume up to 30 fewer watts at idle and 30 more watts under load than the 4870, our testing did not prove out those claims. According to our tests, the Radeon HD 4890 actually consumed slightly less power at idle and under load. The differences were minimal, however.
While the power consumption numbers put the 4890 and 4870 in a similar league, we can say the 4890 runs much cooler than the 4870. Our Asus Radeon HD 4890 cards idled at under 50'C and peaked in the mid 80's under load. But where we noticed the biggest difference was when we removed the cards from the test system. After testing, the Radeon HD 4890 felt very warm to the touch when removing it from the test rig, but the Radeon HD 4870 was so much hotter, it was almost too hot to handle without giving it a few minutes to cool down. Not exactly a scientific data point, but something we wanted to mention nonetheless.
We'd also like to mention that the Radeon HD 4890 is a relatively quiet running card. At idle, the fan on the card is barely audible over the other components in our test system. Under load, the fan does spin up and is audible over the other components, but we would not consider it loud by any means.