The 64-bit Xeon Processor

One month ago Intel officially released their last processor that hadn’t a 64-bit version: Xeon XP. Xeon MP is a processor target to multiprocessor servers with four or more CPUs, based on Pentium 4 microarchitecture.

This new Xeon MP model is also known by its code-name Truland and Intel also has released a new chipset for it, Intel E8500. This new CPU has some new features if compared to the previous Xeon MP model:

  • Clocks from 2.83 GHz to 3.66 GHz.

  • EM64T technology, allowing memory addressing up to 1 TB (it uses a 40-bit address bus). Due to limitations on the memory modules found on the market today, this CPU is limited to 64 GB of DDR2-400 memory. However, with the FB-DIMM memory release this limit will probably increase.

  • 667 MHz external bus.

  • 1 MB L2 memory cache.

  • L3 memory cache up to 8 MB (the exact quantity depends on the model). This memory is locate on the processor’s body, but not in its core (die), but in a silicon chip located besides the processor silicon piece, accessed at 1,066 MHz.

  • xD (Execute Disable) bit, blocking virus from being executed (click here to learn more about this technology).

  • DBS (Demand Based Switching), a feature based on the SpeedStep technology. This feature allows the server’s processors to reduce their clock rate depending on the server load, thus saving energy. For example, if the server is used as a web server, if the traffic drops a lot in the middle of the night , the server will automatically reduce the clock rate of the processors. The saved energy may not seem a lot, but think about a data center with hundreds of server. In this scenario the savings on the electricity bill can be important.

  • RAS (Reliability, Accessibility and Support): Xeon and Xeon MP CPUs allow “memory sparing” and “memory mirroring” techniques, which are also known as “memory RAID”. With the first technology, if the processor finds a defective memory module, it automatically disables that module. This technology goes deeper, allowing the CPU to turn off only the exact memory chip that is defective. With memory mirroring the data available at one memory module is replicated to another memory module in real time. If one of the memory modules goes defective, the backup module is still running and there is no data loss. Xeon MP, contrary to the “plain” Xeon, allows memory module replacement with the server up and running (“hot swap”). With Xeon processor it is necessary to turn the server off before replacing the memory modules.

  • Enhanced Defer Bus Protocol: Allows one processor to forward tasks to another processor on the system, feature not available on the “plain” Xeon.

  • Virtualization technology: This new processor and the new Intel E8500 chipset support Intel’s virtualization technology, also known as Vanderpool. This technology allows the system to be divided (“partitioned”) into several independent machines.

  • Pellston technology: This technology disables part of the memory cache that are giving too many ECC errors, for two reasons. First, speed. At each ECC error time is lost correcting the corrupted data. Secondly, if a memory area is giving too many ECC errors this probably means that it is not so good and can burn at any time soon.

  • Foxton technology: Dynamic overclocking technology, if the processor requires an extra performance during load peaks. It is the first time we see a CPU manufacturer officially doing an overclocking technique.


Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.