Last summer, we saw a monumental shift in the way AMD does business in the graphics card market.  Instead of chasing after a large, monolithic graphics solution for the high-end, AMD instead opted for a smaller technology that would offer scalability in both directions.  That solution was the RV770, and it spawned one of the most successful launches in AMD/ATi's history.  The 4870, 4850, and 4830 video cards filled out the mid-range portion of AMD's lineup, and for the high end, AMD placed two of these chips on the same PCB, and created the 4870X2 and 4850X2 cards.  AMD calls this their "sweet spot" strategy, and it seems to be working.  In fact, filling five SKUs with a single piece of technology has done a good job keeping AMD's graphics unit in the black, and that is difficult to do in these crazy times. 

It has worked so well, in fact, that the successor to the RV770 will actually not be replacing the successful chip; it will only further augment AMD's product line.  That successor is here today, and it is known as the RV790, packaged in the newest AMD GPU, the Radeon HD4890. 

What is the RV790?

Many people will be surprised that the RV790 is actually not that much different than the RV770 that preceded it.  The RV790 offers no new architectural advancements, and it is not a die shrink.  So what makes the RV790 different than the RV770?  The answer lies in the layout of the chip itself.  When a digital circuit is being designed with the intention of hitting speeds of several hundred megahertz, layout is incredibly important.  In fact, the layout itself can be an inhibition to high clock speeds.  That apparently was the case, as when AMD re-timed the chip, it found that it was able to significantly improve not only the speed bins of the processor, but also the power consumption as well.  The findings obviously were not only significant enough to warrant a new revision, but a new graphics card as well. 

So where does the HD4890 reside in the AMD landscape?  The 4870 and 4850 based cards both recently received price cuts, hitting the $169 and $129 price points.  This means the 4890 is now expected to hit the upper range of $249-$259.  The 4870X2 still fits the high end market, with a price point at the sub $500 level.  I would love to see a 4890X2 replace the 4870X2 at the high end, however there are currently no plans for such a card according to AMD. 

The specs for the 4890 follow in with what we would expect for an higher clocked version of RV770.  The most interesting aspect is the power usage; the 4890 uses an additional 30W under load, but 30W less in idle.  Keep in mind that this is only the reference clocks, as many of the OEMs are also planning over clocked editions of the 4890.  Sapphire is  among them, with plans to release the HD 4890 OC Edition with a 901MHz core clock and 1GHz memory clock.