A few months ago AMD launched a series of revised Phenom processors that use the B3 stepping. This revision cures the TLB problem that blighted the original launch of Phenom and also increases the speed that the processor can reach. Phenom X4 9550 and 9750 effectively replaced the original 9500 and 9600 but AMD also added some other models to broaden the product range.
Ed has covered the faster 2.5GHz Phenom X4 9850 Black Edition and also the novel tri-core Phenom X3 8750 but that's not the end of the story. AMD also recently launched two low power models of Phenom in the shape of the X4 9350e and 9150e. They run at 2.0GHz and 1.8GHz respectively and share most of their features with the other quad core X4 models of Phenom. Namely the 65nm SOI fabrication process, a transistor count of 450 million, 512KB of L2 cache per core, 2MB of shared L3 cache and a 128-bit DDR2 memory controller.
The key feature of the lower power Phenoms is the reduction in Thermal Design power (TDP) from 95W to 65W which is a significant drop in anyone's book. AMD has made this improvement in heat output essentially by reducing the clock speed, which means a lower voltage and thus less power is required to keep the chip running. AMD didn't have a clean sheet of paper when it designed the Phenom 9350e. On the one hand it was constrained by the performance of the low power dual core Athlon X2 4850e which runs at 2.5GHz with a TDP of 45W. It was essential that the low power quad core Phenom would out-perform the Athlon X2.
On the other - rather larger - hand we have Intel. The all-conquering Core 2 Q6600 runs at 2.4GHz and overclocks like a dream, and in the process it makes Phenom look a bit silly. To add insult to injury Intel has reduced the price of Q6600 to £125 where it is in direct competition with Phenom. The one thing you can say against Q6600 is that it has a relatively high TDP of 105W. It's important to be clear that TDP isn't the same thing as power draw or heat output but instead it's a worst case scenario for PC builders and system designers. Although Q6600 appears quite juicy you can keep it under control with a modest cooler that is nice and quiet. In our experience a Phenom X4 9750 or 9850 with a TDP of 95W has a similar power draw to Q6600 and requires a noisier cooler.
But that's yesterday's news as Q6600 uses a 65nm fabrication process while Intel has shifted to its new 45nm Penryn process. The nearest equivalent to Q6600 is the Q9300 which runs slightly faster at 2.5GHz yet it has a lower 95W TDP. Admittedly the cost is higher than Phenom at £175 but that's a relatively small detail so AMD has been forced to find a way to differentiate Phenom from the Penryn Core 2 Quad and the result is the low power Phenom.