AMD - Phenom X4 9850 Black Edition review

AMD's first stab at a quad-core processor was a bit of a turkey, as Phenom was plagued by a TLB (Translation Lookaside Buffer) error that required a temporary fix before the processor could be launched. Although none of us were clear about the function of the TLB, we rapidly learnt that the hot fix for the problem cleaved 20 percent off the performance of Phenom.

This was a particular problem as the first Phenoms ran at clock speeds of 2.2GHz and 2.3GHz, which were too slow to compete with Intel Core 2 Quad, and the TLB fix cut performance even further.

Phenom X4 is a revision of the original Phenom which fixes the TLB error and also raises the clock speed. The X4 part of the model name is significant and AMD has launched a Phenom X3 range, which is unusual as it is the world's first tri-core processor (as far as we know; if you know better please drop us a line).

Phenom X4 is further distinguished from the original Phenom by the addition of a '50' suffix to the model code, so a Phenom 9500 is an original B2 quad-core 2.2GHz processor while a Phenom X4 9550 is a revised B3 2.2GHz CPU with a fixed TLB.

In addition you can get a 2.4GHz Phenom X4 9750, the 2.5GHz Phenom X4 9850 Black Edition that we're reviewing here and the top-of-the-range 2.6GHz Phenom X4 9950 Black Edition.

The specifications of these processors are quite telling, as both Phenom X4 9550 and 9750 have a TDP of 95W which is in line with earlier models of Athlon 64. But the Phenom X4 9850 has a TDP of 125W and the X4 9950 has a TDP of 140W.

There's another difference as the X4 9750 has a HyperTransport speed of 1.8GHz while the X4 9850 operates at 2GHz. These figures strongly suggest that AMD has pushed the architecture of this 65nm processor to its limits as the TDP is rising rapidly while the clock speed is only making modest advances.

Phenom uses the same Socket AM2+ form factor as the last Athlon 64 processors which used DDR2 memory and now that the bugs have been sorted it is a decent processor. The problem is that the latest 45nm Penryn Core 2 processors perform better clock-for-clock and the Intel processors also overclock significantly better than the new Phenom. We've read reports of Phenoms that overclock to 3GHz but were only able to get our 2.5GHz Phenom X4 9850 to run at 2.69GHz, which is an increase of less than ten percent.

This also puts AMD in something of a quandary. If you want a fast AMD processor the dual core Athlon 64 X2 is still a decent chip. On the other hand if you're using an AMD 780G chipset in a Media Centre PC you won't want a powerful quad-core Phenom. The upshot is that Phenom falls between two stools as it has an apparent inability to overclock significantly yet it isn't especially cheap compared to Intel Core 2 Duo and Quad.