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What's in the cards
Initially, the Radeon HD 4800 series will come in two forms, powder and rock. Err, I mean, 4850 and 4870. By now, you may already be familiar with the 4850, which has been selling online for a number of days.

Here's a look at our review sample from Sapphire. The stock clock on the 4850 is 625MHz, and that clock governs pretty much the whole chip, including the shader core. These cards come with 512MB of GDDR3 memory running at 993MHz, for an effective 1986MT/s. AMD pegs the max thermal/power rating (or TDP) of this card at 110W. As a result, the 4850 needs only a single six-pin aux power connector to stay happy.

Early on, AMD suggested the 4850 would sell for about $199 at online vendors, and so far, street prices seem to jibe with that, by and large.

And here we have the big daddy, the Radeon HD 4870. This card's much beefier cooler takes up two slots and sends hot exhaust air out of the back of the case. The bigger cooler and dual six-pin power connections are necessary given the 4870's 160W TDP.

Cards like this one from VisionTek should start selling online today at around $299. That's another hundred bucks over the 4850, but then you're getting a lot more card. The 4870's core clock is 750MHz, and even more importantly, it's paired up with 512MB of GDDR5 memory. The base clock on that memory is 900MHz, but it transfers data at a rate of 3600MT/s, which means the 4870's peak memory bandwidth is nearly twice that of the 4850.

Both the 4870 and the 4850 come with dual CrossFire connectors along the top edge of the card, and both can participate in CrossFireX multi-GPU configurations with two, three, or four cards daisy-chained together.

Nvidia's response
The folks at Nvidia aren't likely to give up their dominance at the $199 sweet spot of the video card market without a fight. In response to the release of the Radeon HD 4850, they've taken several steps to remain competitive. Most of those steps involve price cuts. Stock-clocked versions of the GeForce 9800 GTX have dropped to $199 to match the 4850. Meanwhile, you have higher clocked cards like this one:

This "XXX Edition" card from XFX comes with core and shader clocks of 738 and 1836MHz, respectively, up from 675/1688MHz stock, along with 1144MHz memory. XFX bundles this card with a copy of Call of Duty 4 for $239 at Newegg, along with a $10.00 mail-in rebate, which gives you maybe better-than-even odds of getting a check for ten bucks at some point down the line, if you're into games of chance.

Cards like this "XXX Edition" will serve as a bridge of sorts for Nvidia's further answer to the Radeon HD 4850 in the form of the GeForce 9800 GTX+. Those cards will be based on the 55nm die shrink of the G92 GPU, and they'll share the XXX Edition's 738MHz core and 1836MHz shader clocks, although their memory will be slightly slower at 1100MHz. Nvidia expects GTX+ cards to be available in decent quantities by July 16 at around $229.

For most intents and purposes, of course, these two cards should be more or less equivalent, including performance. The GTX+ shares the 9800 GTX's dual-slot cooler and layout, as well. As a result, and because of time constraints, we've chosen to include only the XXX Edition in most of our testing. The exception is the place where the 55nm chip is likely to make the biggest difference: in power draw and the related categories of heat and noise. We've tested the 9800 GTX+ separately in those cases.

Nvidia has also decided to sweeten the pot a little bit by supplying us with drivers that endow the GeForce 9800 GTX and GTX 200-series cards with support for GPU-accelerated physics via the PhysX API. You'll see early results from those drivers in our 3DMark Vantage performance numbers.