The RV790 GPU: ATI Not Moving to 40nm Yet?
There has been increasing speculation since the beginning of 2009 that ATI will soon release a 4900 series product line-up. As is often the case with GPUs, this will not be a major change from the chip has already been used in the various 4000 series products. That said, the fact that ATI is not re-vamping the architecture doesn’t mean there wont be a major increase in performance or efficiency, and considering that Nvidia has fleshed out its high-tier products with an array of fast single-chip designs, there is certainly reason for ATI to want to pursue a quicker chip. In the Radeon 4890 ATI partially delivered this in the RV790, which made changes that will be explained below. But the RV790 was widely expected to debut in a 4900 series product, not as a the Radeon 4890, raising questions about future ATI cards.
The RV790: Evolution
Evolution is common in graphic chips. It is arguable that there hasn’t been a major single architecture change since the original GeForce cards debuted. GPUs tend to incorporate elements from previous generations into new products, adding or changing small elements rather than significantly revising the entire GPU. The same is true with the RV790, which has many attributes in common with all other RV700 series GPUs.
There are some differences, however. These differences are the result of problems ATI was having with getting the RV770 to reliably exceed the performance of previous Radeon 4870 products. To increase the performance that could be squeezed from a single GPU, ATI made internal tweaks to the power distribution and the timing of the GPU, in addition to adding a larger number of “decoupling capacitors”, which are elements of a processor which help improve signal quality. These changes are all minor, but its obvious that they have succeeded, as they’ve set the stock clock-speed of the 4890 at 100 mhz higher than that of the 4870, an increase of about 13 percent.
As a result, the new 4890 is considered to be a contender to the GTX275, which also means that the Radeon 4890 is not that far off from a GTX280. While simply increasing the clock speed isn’t a significant change, it does appear that they’ve been able to squeeze out the extra performance with minimal effort, a result ATI is likely happy with.
Small Things In The Future
One thing that the RV790 does not do is move from a 55nm to a 40nm process. There was speculation that it would be a 40nm GPU, and it has long been rumored that ATI is ready to move everything over to 40nm.
For AMD, this will just serve to further boost their bottom line. Although few outside of ATI know exactly how much of a profit the company makes on each 4000 series card, it is widely thought that ATI’s smaller GPUs has resulted in a big jump in profit per unit, which seems to be reinforced by ATI’s willingness to keep pressing a price war against Nvidia, whose much larger GPUs are undoubtedly more expensive to make.
But consumers also benefit from the jump to the 40nm processor, and while the RV790 has not gone 40nm yet, ATI has dipped its toe in the water with the less powerful RV740. The RV740 arrived in the new Radeon 4770, which has just hit retailers, and it does use the 40nm process. Currently, the Radeon 4770 is the only product available from either ATI or Nvidia with a chip manufactured on a 40nm process. Besides the benefits to ATI’s bottom line, the smaller manufacturing process means a GPU which runs cooler and uses less energy, and the 4770 is the case in point. Compared to an array of other cards available on the market, the Radeon 4770 is consistently cooler, quieter, and more efficient than its peers. That being the case, it is likely that future Radeon 4900 series products will be surprisingly practical. The 4850 and 4870, as good as they are, ran hot in their original incarnations, resulting in the popular conception that ATI cards run hot.
It is somewhat odd that ATI has chosen to go with the RV740 as their first 40nm GPU rather than the higher-end RV790. Generally, high-end products receive attention first, and even AMD has usually gone that path by hitting retailers with high-end versions of a new product first, then following up with lower-clocked versions of the same architecture. The decision to go to 40nm with the RV740 could be related to problems with the foundary used by ATI, which continues to transition into 40nm production. It is interesting that Nvidia is reporting it will start moving to the 40nm process with its notebook GPUs first, which are also lower-performance parts, and Nvidia uses the same foundry.
Short Term Speculation
In the short term, the next new high-performance cards from ATI will likely all use the RV790, and the transition to 40nm will occur gradually over the next quarter. It is extremely likely that ATI will finally begin to lay down a 4900 series and populate it with cards based off a 40nm RV790. This will include dual-GPU cards using the RV790.
Beyond that, things get more sketchy. AMD has been very discreet of late, both in the AMD processor division and in the ATI graphics division. The Phenom II debuted with almost no fanfare not only because most people weren’t expecting a great deal, but also because AMD seemed incredibly hesitant to reveal exactly what it was planning to do. The Radeon 4000 series cards also arrived under a cloak of secrecy, with little being announced of even leaked to the press beforehand.
In other words, it’s extremely hard to say how ATI’s next generation - which should be the 5000 series - will different from the current GPUs. We can at least say for sure that ATI’s strategy of small, high-power GPUs will remain that same. Whatever comes out of ATI, it will be aimed at the mass-market first.