Board analysis

At first glance the Radeon 5850 looks very similar to the Radeon 5870, but ATI’s made some changes to the board that should make it more accommodating to end users.

Size comparison: Radeon 5850 and GeForce GTX 285

Size comparison: Radeon 5870 sits up top while the 5850 rests below

Most notably is the size of the board itself. Like previous high-end graphics cards from ATI, the Radeon 5850 measures 9.5” in length. This makes it nearly 1.5” shorter than the Radeon 5870, and about 1” shorter than the GeForce GTX 285 from NVIDIA. This should make life easier for those of you with smaller cases: the Radeon 5870 is so long it could interfere with the power/data cables of your hard drive(s) in some system cases.


With its shorter PCB, ATI places the two power connectors on the end of the board, similar to the Radeon 4870 and Radeon 4890.

The cooling system itself is pretty similar to the Radeon 5870. Like the 5870, the Radeon 5850 employs a quad-heatpipe cooling design. The heatpipes are made from copper to increase their effectiveness, just like the Radeon 5870. Three of the heatpipes are used to draw heat off the GPU, while the fourth rests over the voltage regulators. Speaking of the VRMs, ATI employs newer regulators that send temperature info to the GPU, so it can monitor temps of the regulators and adjust clocks to prevent overheating.

A dual-slot aluminum heatsink (with copper base plate) is used to draw heat off the GPU. Obviously the heatsink used isn’t as large as the unit found on the 5870, but with fewer shaders cranking along at slower clocks, it doesn’t have to be as large either.

The fan itself is the same part used on the Radeon 5870. The new fan ATI employs on their 5800 series cards is outfitted with quieter bearings; audibly the fan’s tone is lower, making it easier on the ears than previous ATI designs. It also spins at just 1200 RPMs at idle versus the 1600 RPMs used on the Radeon 4890 fan.


The end result is a card that runs eerily quiet. Even when two cards are combined for CrossFire, noise output remains respectable; right around 54 decibels in our testing.

Despite its increase in transistors and faster clocks, the 5800 series are able to run cooler and quieter than their predecessors thanks in part to the smaller 40-nm manufacturing process, but also thanks to new low power modes that reduce clock speeds and voltages more aggressively than ever. At idle the 5850 runs at just 157MHz core/300MHz memory and consumes just 27W of power.

One difference between the 5870 and 5850: Radeon 5850 cards skip the backplate

5850+5870 CrossFire

One neat trick ATI GPUs have supported for the past two generations is the ability to mix and match graphics cards from the same family together. This tradition continues with RV870, as we were successfully able to combine our Radeon 5850 board with the 5870 for 2-Way CrossFire.

When the two cards are combined for CrossFire, each card runs at its own independent clock speeds and SIMD configuration. In other words, the 5850 doesn’t OC itself to 5870 speeds nor does the 5870 underclock itself to 5850 speeds or disable two SIMDs. Performance was only up only marginally over the 5850 CrossFire configuration however, suggesting a potential quirk in the driver. We’ll have to investigate this more thoroughly when time warrants.

DiRT 2 and availability

Like the 5870, Radeon 5850 boards will be bundled with vouchers to download DiRT 2 once it arrives in November. We’ve also been told that cards will be hitting retailers shelves beginning today.

Like the 5870, availability is going to be very tight. Supply won’t be sufficient to meet demand. So if you want one of these boards, you better have a fast internet connection constantly refreshing your favorite retailers and good eye/mouse coordination.