AMD bests Nvidia with graphics chip strategy

Advanced Micro Devices' bet on a new approach to graphics chip design appears to be paying off, according to analyst Jon Peddie. This could put AMD's ATI graphics chip unit on top again--or at least on equal footing with Nvidia, the graphics leader over the last few years.

Peddie heads Tiburon, Calif.-based Jon Peddie Research, which specializes in graphics chip market research.

Test reports on AMD's and Nvidia's newest graphics chips are pouring in. Both companies are racking up good scores. (See Diamond Viper Radeon HD 4850 review here.)

But beyond the day-to-day test scores, AMD's ATI graphics chip unit may be winning the longer strategic battle. ATI has gambled on a radically different strategy for its latest series of chips--the HD 4850, HD 4870, and upcoming dual-chip R700.

"(AMD) is starting in the middle of the market and scaling up. That's a break with tradition," said Peddie. "We always started at the very, very tippy-top and build the most powerful thing you could and then let it scale down over time."

But Peddie said this traditional approach just isn't practical anymore. "The chipsets keep getting larger and larger despite the fact that we were going to smaller and smaller (manufacturing) process nodes. The chips grew faster than the process nodes shrunk and the consequences of that is that the power consumption went up, the costs went up, and it got to the point where it's kind of impractical to continue along that way," he said.

In essence, AMD's ATI unit strategy is to build smaller, less power-hungry chips and then gang them up to get better performance. Nvidia's strategy has been to build one large, extremely fast--and extremely power hungry--chip.

For ATI, the execution of this chip-ganging strategy is the key. And this is where ATI appears to have been successful. "The inter-processor communications. Getting that to work has been the trick. This is what ATI has done. They've come up with this stellar way of doing inter-processor communications so they can in fact get the scaling," according to Peddie.

And there's more than meets the eye. ATI has also cut in half the number of bits in the memory interface, Peddie said: down to 256 bits while Nvidia has remained at 512. "That has the benefit to ATI of reducing a big hunk of the power consumption."

Peddie said in the past this kind of approach would have been suicidal because it would have decimated ATI's test scores. "The argument against this is that graphics performance is a function of memory," he said. "Typically you want wider and wider (bit width)."

But ATI has countered this by using the fastest memory standard available. "So to compensate for shrinking down the bit width, ATI has jumped to the next-generation in memory design called GDDR5. GDDR5 is approximately three times faster than GDDR3--which is what Nvidia is still using and what ATI uses on their smaller cards," according to Peddie.

"So with three times the speed but half the width, they end up with 1.5 times the processing capability with the memory."

"A very clever thing that they did but mind you it was a gamble that looks like it's going to pay off," he said.

ATI has more processing units than Nvidia inside its chip too. "The other thing is that ATI has 800 processors in their chip and Nvidia has 240. That has a processor count advantage," Peddie said.

Though it remains to be seen if this advantage is borne out in testing over time, he added. "Nvidia and ATI keep improving their drivers so they'll seesaw back and forth with their scores, almost from week to week."

But in the long run, Nvidia may be forced to adopt ATI's strategy to keep pace in these week-to-week battles. "If ATI is successful, as we expect that to be, then Nvidia will have no choice but to adopt (ATI's) approach, just out of practicality," Peddie said. "It just makes a whole lot of sense."

AMD-ATI's upcoming R700 (rumored to be called the 4870 X2) two-chip graphics board will be the ultimate test of this strategy.

"It's a new proprietary inter-processor communication technology. If they put these two chips on one board and it does scale properly, then they have pulled off a coup," he said.

"When you gang up graphics chips (using the traditional Scalable Link Interface or CrossFire technologies) they roll off pretty fast. ("Roll off" implies that performance doesn't scale up well.) "So when you put two boards in, you don't get twice the performance but you (only) get one and a half. You put four boards in and you (only) get about 1.7, 1.8. What ATI is saying is that with two chips using (their) proprietary inter-bus, they will get 1.8 (the performance) with two chips. If that's true, you can expect to see four of them giving you something around 2.5."

Getting 2.5 times the performance from four boards would be a masterstroke for ATI.

The previous ATI dual-chip solution was very different, Peddie said. "The HD 3870 X2 was not a proprietary bus but a CrossFire connection. The CrossFire connection and the SLI connection are at the very, very end of the pipeline. Not the most efficient place to do an inter-processor communication. That's one of the reasons ATI has abandoned it."

AMD's ATI unit is also better positioned than it was before in manufacturing. "Part of the reason that Nvidia has been ahead is that ATI has been suffering over the last three or four years with manufacturing problems. It's not that ATI didn't have a good chip, the problem was that ATI couldn't build enough of them."

This should change with the newest series of chips. "This (design)--so they say--will really go into high-volume production." Though he cautioned this still remains to be seen.

"The (new ATI chip) is a really efficient, tight design. They used to do this all the time but they kind of got off that trail. And now they're back on it."