AMD drops Athlon in favour of Phenom

Posted at: 12:00am 14th May 2007 by Ben Hardwidge

In a bout of Core-induced panic, Intel nemesis AMD has informed us that it will phase out the Athlon brand on its next generation of top-end K10 CPUs in favour of a new brand, Phenom.

According to AMD's marketing bumph, the CPUs will 'allow users to experience the phenomenal'.
It's a shame that AMD feels the need to cover up the details with marketing speak, as the K10 architecture looks set to be pretty damn good.

The first CPU to be based on the architecture will be an Opteron featuring the Barcelona core. At the top of the list of Barcelona's new feature set is a radically different cache architecture, which has no less than three integrated levels of cache inside the CPU. Each of the four cores will have 64KB of Level 1 cache, followed by a larger 512KB block of Level 2 cache. However, these independent Level 2 cache blocks will then feed into a 2MB shared pool of Level 3 cache.

This differs from Intel's Core 2 architecture, which has only a large, shared pool of Level 2 cache after the Level 1 cache. Guisseppe Amato from AMD explained to Custom PC that the reasoning for the independent Level 2 cache for each core was to cut down latency. Basically, if one core wants to write an instruction to the shared cache but is unable to do so because the cache is being read by another core, it can now simply store that instruction in the Level 2 cache and drop it in when it can.

The new architecture will be able to handle up to four floating-point operations per clock, and will also feature improved branch prediction and support for 128-bit SSE instructions. However, unlike Intel's forthcoming Penryn products, the K10 architecture will still be fabricated on a 65nm process. According to AMD, this is due to the total amount of cache on the processors being lower than that on Intel's processors, which frees up enough room to fit a 65nm quad-core CPU in a single package.

After that will come desktop parts in the form of the quad-core Phenom FX, and the Phenom X4 and X2. These will feature the same cache architecture as that of the Opteron, and will be able to accommodate the same amount of cache. However, there are some slight differences between the Phenom and the Opteron. The most significant of these is that overclockers will be able to adjust the frequency of each core separately, although the vcore will always remain at the same level as the most heavily loaded core.

However, unlike Opteron CPUs, Phenom CPUs will allow you to adjust the voltage of the memory controller separately from the CPU cores. This feature is courtesy of AMD's new Socket AM2 +, which provides two separate voltages for the memory controller and CPU. Phenom FX CPUs will use Socket F, and will be backwards compatible with AMD's existing Quad FX motherboards, meaning that you could build an 8-core system with two quad-core CPUs. The Phenom X2 and X4 will use AMD's AM2+ socket, although you'll be able to use the CPUs in a current AM2 motherboard too; you just won't have access to the new socket's extra voltage features. The new desktop CPUs are planned for release later this year.