For a time AMD took a technical lead over Intel with Athlon 64, but that lead came to an abrupt end when Intel launched its superb Core architecture.

There's no denying that Core 2 Duo and Core 2 Quad are superb processors but AMD's engineers have plenty of reason to feel proud of their achievements. Opteron and Athlon 64 were the first processors with the capability of running 32-bit and 64-bit software and they also included a memory controller which speeds up communication and reduces the complexity of the chipset and motherboard.

Intel picked up on the 64-bit feature for Pentium D and Core 2 but hasn't yet moved the memory controller out of the chipset and into the processor core, although it's only a matter of time until it does. On the other side of the coin, Intel was the first processor company to launch a range of quad-core CPUs, but there's a bit of a dispute about this technical feat. Intel does indeed pack four cores into Core 2 Quad but they're arranged as two dual-core dies in a single processor package.

This has allowed AMD to claim another technical first by launching the world's first genuine quad-core processor in the shape of the Phenom. In appearance this new processor looks very similar to Athlon 64 and is backwards compatible with the AM2 socket that is used on Athlon 64 motherboards. These are the models which use DDR2 system memory, rather than the Socket 939 models which use DDR memory.

In many respects Phenom is a die shrink of Athlon 64 that has moved to a 65nm fabrication process with those all-important four cores. Other changes include a move to Cool'n'Quiet 2.0 along with support for DDR2-1066 memory.

There is a total of 2MB of L2 cache with 512KB for each core plus 2MB of L3 cache which is shared between the four cores. The Hyper Transport bus has moved to version 3.0 with a clock speed of 3.6GHz and a raw bandwidth of 20.8GBps compared to the 6.4GBps that we saw with HyperTransport 1.0 on Athlon 64.

Phenom uses a processor socket called AM2+ which is pin-compatible with AM2 but if you want Hyper Transport 3.0 you need to use Phenom with an AM2+ chipset such as the AMD 790 or AMD 790FX, rather than an AMD690 or Nvidia nForce 590 SLI which will reduce the connection speed to Hyper Transport 1.0.

Our testing showed that mixing and matching processors and motherboards was a poor idea. You'll lose performance if you plug a Phenom into an older motherboard but you also lose out if you use an Athlon 64 X2 in a new AMD 790 FX chipped motherboard.

AMD had planned to launch Phenom at three speeds. The Phenom 9500 runs at 2.2GHz, the 9600 is 2.3GHz and the 9700 was due to have a clock speed of 2.4GHz, however AMD cancelled the launch of the fastest version at the last moment. The problem, according to AMD, relates to the Translation Lookaside Buffer and L3 cache but that doesn't explain why it only applies to one model and not to the whole Phenom family.

Although AMD can correctly claim that it has the first quad-core processor, it is clearly lagging behind Intel in other areas. The 65nm process used in Phenom is one generation behind the 45nm Intel Penryn and the support for DDR2-1066 memory looks a bit antique compared to the DDR3-1600 support we are seeing on various Intel motherboards.

Both of those points are due to be addressed over the course of the next year with a move to 45nm in 2008 and a Socket AM3 in 2009 which will encompass DDR3-1333, but you can bet that Intel will have also made advances in that time.

The biggest problem with Phenom is its lack of performance. The 2.3GHz Phenom 9600 is too slow and doesn't have the same performance as a 2.4GHz Core 2 Q6600 which sells for the same price, while the faster Intel processors that zip along up to 3.2GHz destroy Phenom on performance.

To add to AMD's woes, the Phenom barely overclocks even with the assistance of AMD's funky new OverDrive utility, while Intel's processors can usually handle an extra Gigahertz of clock speed.

AMD has priced its new Phenom 9600 to match Intel Core 2 Q6600 but it loses the battle in every respect. The Intel processor has better performance, draws less power and overclocks like a dream, which leaves little reason at this stage to consider buying a Phenom.