IBM 8687 Installation Guide - Page 30

Advanced Dynamic Execution The Pentium III Xeon processor has a 10-stage pipeline. However, the large number of transistors in each pipeline stage means that the processor is limited to speeds under 1 GHz, due to latency in the pipeline. The Xeon Processor MP has a 20-stage pipeline, which can hold up to 126 concurrent instructions in flight and up to 48 reads and 24 writes active in the pipeline. The lower complexity of each stage also means that future clock speed increases are possible. It is important to note, however, that the longer pipeline means that it now takes more clock cycles to execute the same instruction when compared to the Pentium III Xeon. Comparing the Xeon Processor MP with the Pentium III Xeon and current operating systems (Windows 2000, Linux with 2.4 kernel), good rules of thumb are: - 1.5 GHz Xeon Processor MP/512 KB L3 ≈ 5-20% faster than 900 MHz 2 MB L2 Xeon - 1.6 GHz Xeon Processor MP/1 MB L3 ≈ 15-35% faster than 900 MHz 2 MB L2 Xeon The next generations of operating systems will likely improve performance of the MP processor as they take advantage of the NetBurst architecture. These include Windows .NET and the Linux 2.5/2.6 kernels. For more information about the features of the Xeon Processor MP, go to: http://www.intel.com/design/xeon/xeonmp/prodbref 1.4.2 Intel Xeon Processor DP The Xeon DP is similar to the Xeon MP and is also based on the Intel NetBurst micro-architecture. The Xeon DP was designed by Intel to be suitable only in uniprocessor and two-way SMP processor systems. However, with the use of the IBM XA-32 chipset, the x440 can have up to four Xeon DP processors installed. The Xeon DP models of the x440 models use 2.4 GHz processors, part 37L3533. The key differences between the processors are listed in Table 1-2. Table 1-2 Differences between the Xeon DP and the Xeon MP Feature Xeon Processor DP Maximum CPUs per SMP Expansion Module Two Maximum CPUs per x440 node Four Xeon Processor MP Four Eight 16 IBM ^ xSeries 440 Planning and Installation Guide