Disregarding today's obligatory features such as 64-bit support, virtualization technology or power-saving functions, AMD's and Intel's microprocessors are entirely different. AMD places emphasis on SOI manufacturing (Silicon on insulator) in 90 nm and it relocates the memory controller from the chipset into the processor core. Both helps to increase energy efficiency: SOI reduces leakage currents that cause thermal resistance; the integrated memory logic shortens data paths between the CPU and the memory, while running at the processor's clock speed. Also, each AMD processor in SMP environments (symmetric multi-processing) has its own memory controller. Hence the memory bandwidth scales beautifully if you add processors, which results in great performance.

Intel pairs a classic processor design with high manufacturing efficiency: Most processors are produced using 65 nm technology and will be using 45 nm probably by the end of 2007. Small transistor structures allow the firm to add more cache to processors, or to increase the core count, or even both. Strained silicon technology, which applies silicon germanium layers in order to stretch the atomic structure, eases electron migration, which is beneficial for reaching high clock speeds. To control leakage current Intel pays close attention to maintaining the distances that separate the eight layers of today's processors.

When we said classic design we referred to the memory controller that is part of the chipset northbridge. As a results, its bandwidth is shared between both processors. This may have negative impact in certain scenarios, but it does not require additional memory coherency checks.

There are a couple of important facts noteworthy when comparing the server processors AMD Opteron and Intel Xeon:

AMD Opteron:

It has been the faster processor, especially for floating point operations HyperTransport interconnects processors and core logic. This point-to-point interconnect scales much better than bus interfaces. Power consumption is acceptable even when under load Socket 940 is the basis for all Opteron models that have been released. Usually you can upgrade to one of the dual core models. Each processor has its own memory controller. No FB-DIMM memory is required. Registered DDR400 memory is enough. Quad core Opterons will require a Socket F platform.

Intel Xeon:

The Front Side Bus is the interface and a potential bottleneck between the processor(s) and the chipset northbridge. The 5000 chipset widens this bottleneck by implementing separate Front Side Busser per processor (DIB). Dual core Xeon Paxville DP has high to very high power requirements. Dual Core Xeon Dempsey 5000 has high power requirements. Less flexible platform design: A Xeon Nocona or Irwindale (socket 604) can only be upgraded with a dual core Xeon Paxville DP. If you want a Xeon 5000 (Dempsey) or Xeon 5100 (Woodcrest) you need the 5000 chipset platform for socket 771 (Bensley). Quad channel DDR2 memory controller offers more bandwidth, but requires FB-DIM modules Intel's chipset and FB-DIMM components require more energy than the Opteron equivalents Quad core Xeons are technically feasible for socket 771.