AMD just launched a pair of dual-core Socket AM2+ processors, which may sound like dull news in these days of quad-core CPU power but stick with us as there's a tale worth telling...
We last reviewed a dual core Athlon 64 X2 more than a year ago. This was a 3.2GHz 6400+ model built on a 90nm fabrication process and it drew 1.4V to break the 3GHz mark with the result that it had a TDP of 125W - that's horribly toasty for a relatively lowly dual-core processor. To make matters worse it was clear that AMD's K8 technology was at its limits as the potential for overclocking was non-existent.
So here we are with a new dual-core processor but it has very little in common with the Athlon 64 X2 as it is built on Phenom technology. In effect this makes Athlon X2 a continuation of the Phenom series but instead of calling the new processor Phenom X2 AMD has chosen to continue the well established Athlon name, though the '64' suffix of previous Athlons has now disappeared.
Names are relatively trivial but the hardware is important and the specification of Athlon X2 owes everything to Phenom. The transistor count has climbed to 450 million, just like the Phenom X3 8750 we used as a comparison in our testing, and the TDP is also the same, at 95W.
The Athlon X2 7750 Black Edition has a clock speed of 2.7GHz and sells for around £80inc VAT while the 2.5GHz Athlon X2 7550 is an OEM model that will end up inside budget PCs. There is 512KB of L2 cache per core for a total of 1MB (as this is a dual core processor) and there's also an extra layer of cache, aptly named L3. There's 2MB of this which is shared across both cores.
These new Athlon X2s also use the faster HyperTransport 3.0 connection found in Phenom with a maximum clock speed of 1.8GHz in each direction, instead of the 1GHz speed of Athlon 64. This enables a potential 41.5GB/s of bandwidth, which is double that of the outgoing Athlon 64 X2s.
It is impossible to tell whether AMD has disabled functioning cores to convert a Phenom X4 or X3 to arrive at Athlon X2, whether it is making the most of faulty Phenom cores that are otherwise headed for the scrap heap, or if it's a dedicated dual-core design.
What we do know is that Phenom X4 9750 runs at 2.4GHz (and costs about £125) and Phenom X3 8750 also has a clock speed of 2.4GHz, along with a price of £105. The new Athlon X2 7750 is clocked at 2.7GHz which is even faster than the Phenom X4 9950 which manages a measly 2.6GHz. We can speculate that AMD is able to crank up the speed of the core as it can manage power and heat better in a dual core model than is possible in a quad core Phenom.
The core voltage in Athlon X2 is 1.20-1.25V which lies at the upper range of Phenom's 1.05-1.25V but significantly below the 1.35-1.40V used in Athlon 64 X2 6400+. The integrated memory controller operates with DDR2-1066MHz instead of the DDR2-800MHz that we are used to seeing on dual core AMD processors.