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AMD's Radeon HD 5850 arrives

Say hello to the 5870's smaller, nimbler sibling

At this point, we know AMD's new Radeon HD 5870 graphics processor is very fast—roughly as quick as two previous-gen GPUs put together. We know the 5870 introduces DirectX 11 support, improved anisotropic filtering algorithms, and reborn supersampled antialiasing. We know the card actually draws less power than the older Radeon HD 4890, both at idle and under load.

We shared all of those discoveries last week in our review of the Radeon HD 5870.

If you've read that review, you'll also know about the 5870's formidably long circuit board and its relatively onerous $379 price tag. Those aren't surprising attributes for a top-of-the-line graphics card, but they definitely call for a more mainstream derivative. That's where the Radeon HD 5850 comes in. With a $259 suggested retail price and a shorter board, the 5850 serves up a slightly diluted version of the 5870's potent cocktail. Let's see if it goes down any easier.

Cypress sheds a couple of branches
Lift the 5850's cooler, and you'll find the exact same 40-nm Cypress graphics processor that powers the 5870. AMD has made a few adjustments to go along with the 5850's lower price tag and smaller footprint, however. First, it's disabled two of Cypress' 20 SIMD arrays and two of the texture units that accompany each array. Since every SIMD array includes 80 ALUs, or stream processors, and each texture unit can churn out four texels per clock, this change takes us down from 1600 SPs and 80 texels/clock on the Radeon HD 5870 to 1440 SPs and 72 texels/clock on its little brother.

AMD has also reduced clock speeds to keep the 5850 from flying too close to the sun. Where the 5870's GPU ticks away at 850 MHz with its memory at 1200 MHz (for an effective 4.8 Gbps data rate), the 5850 runs at 725 MHz with 1000 MHz (or 4 Gbps) RAM. Both cards have the same amount and type of memory, though: 1GB of GDDR5. Considering the resolutions and quality options available in the latest PC games, 1GB seems like the bare minimum for an enthusiast graphics solution. Even the aptly named Radeon HD 4870 1GB comes with that amount by default, and it's selling for less than $150 these days.

Viewed from the outside, the Radeon HD 5850 looks pretty much like a shorter 5870. Makes sense, right? The new card has a similar Batmobile-style cooler dressed in black and red hues, but its PCB is a more manageable 9.5"—an inch shorter than the 5870 and the same length as the old 4870. No need to take a hacksaw to your hard-drive cage with this one. You'll still need a pair of six-pin PCI Express power connectors, though.

The reference 5850 also has the same port configuration as its big brother; a pair of vertically stacked DVI outputs share the ride with DisplayPort and HDMI 1.3a connections. These ports should allow you to use up to three displays simultaneously, just like on the 5870. As we explained last week, AMD's Eyefinity technology presents such triple-monitor configs to the operating system as one ultra-wide display, so many existing games will happily stretch across.

What kind of competition is this newcomer facing? Technically speaking, the 5850 has no direct rivals, since it's one of the only two DirectX 11 graphics processors on the market today (the other being the 5870). However, Nvidia offers two DX10 cards in the same neighborhood. There's the GeForce GTX 285, which has recently dropped to $295.99 after rebate at Newegg, and the slower GeForce GTX 275, which can be nabbed for as little as $209.99. We'll be contrasting the 5850's performance with the faster of those two GeForces today.

Before we move on, readers unfamiliar with AMD's new DirectX 11 graphics processor would do well to peruse our initial look at the Radeon HD 5870. That piece includes all the details and diagrams you'll need to help wrap your head around the Cypress GPU. If you're already well-versed in the particulars of AMD's latest graphics processor, read on for our look at how it performs in the Radeon HD 5850.