Compaq PW5100 Supplementary Manual page 5

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Dual-Peer PCI Buses
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The Compaq Professional Workstation 5100 also uses dual-peer PCI buses to increase system I/O
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. . bandwidth. A single PCI bus provides I/O bandwidth of 133 MB/second that must be shared by
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many key peripherals such as the graphics controller, hard disk, and NIC. With dual-peer PCI
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buses, each bus can provide peek bandwidth in parallel with the other controller, allowing an
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aggregate I/O bandwidth of 267 MB/second. This provides twice the bandwidth of single bus
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architectures. Also, dual PCI buses allow key peripherals to be connected to separate buses to
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balance overall system throughput.
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Diagram 3: Dual Peer PCI Buses
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Optimized Multiprocessing Support
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Finally, with dual memory controllers and dual peer-PCI buses, the Compaq Professional
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Workstations 5100 is able to deliver optimized multiprocessing support. The Intel Pentium II and
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Pentium Pro processors enable multiprocessor support by including circuitry that determines how
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multiple processors can share the CPU bus. However, most multiprocessing implementations in
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the Windows NT / x86 workstation market take advantage of this support by simply adding an
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additional processor to an already existing desktop design. Compaq takes multiprocessing to the
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next step with the Compaq Highly Parallel System Architecture by enhancing memory and I/O
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bandwidth. Multiprocessor systems designed without the Compaq Highly Parallel System
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Architecture will quickly encounter a bottleneck as the multiple processors try to access the other
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system resources, such as memory and I/O subsystems, that have not been enhanced to
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. . accommodate the additional data traffic. The Compaq Highly Parallel System Architecture
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significantly reduces these bottlenecks by incorporating enhanced subsystem resources, such as
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dual memory controllers and dual peer-PCI buses, to accommodate the increased data traffic from
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the multiple CPUs.
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. . Diagram 4: Multiprocessing Support
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