Manufacture

• The AMD Athlon II X4 635 uses the "X4" designation because it is a quad-core processor, meaning that it has four processing units. Thus it has twice the amount of processing power found with the Core 2 Duo, so named because each entry has two processing units. The "II" designation stands for the Athlon chips using the 45-nanometer manufacturing process. The Core 2 Duo, on the other hand, used the 65-nanometer manufacturing process, resulting in bigger CPUs.
  
  

Speeds

• Each AMD Athlon II X4 635 has a processing speed of 2.9 GHz, while the Core 2 Duo chips provide a processing speed range of 1.8 GHz to 3.33 GHz. The Athlon CPU has a 2,000-MHz -- or 2-GHz -- data transfer speed using AMD's HyperTransport, an interconnecting technology the company used as a faster alternative to the front-side bus interface. The Core 2 Duo processors rely on the FSB, which provides speeds of 800 MHz, 1,066 MHz and 1,333 MHz.
  
  

Cache

• Each AMD Athlon II X4 635 and Intel Core 2 Duo desktop processor have two caches: a Level 1 cache and Level 2 cache. These are small components that provide computer data to the processor in a quicker fashion than the system memory. AMD lists the storage capacity of the L1 and L2 cache of the 635 as 512 KB and 2 MB, respectively. Intel gives the storage choices of the Core 2 Duo's L2 cache as 2 MB, 3 MB, 4 MB and 8 MB.
  
  

Power Consumption and Technologies

• The AMD Athlon II X4 635 has a peak power consumption rating of 95 watts. The Core 2 Duo, by comparison, is more energy-efficient, since every CPU in that division has a 65-W rating. Both chips, however, use a 64-bit instruction set. Also included on the Athlon and some Core 2 Duo processors is virtualization technology for integrating several operating systems into a single desktop for using its CPU resources.