Compaq 6000 Supplementary Manual page 5

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Dual-Peer PCI Buses
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The Compaq Professional Workstation 6000 also uses dual-peer PCI buses to increase system
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I/O bandwidth. A single PCI bus provides I/O bandwidth of 133MB/second that must be shared
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by many key peripherals such as the graphics controller, hard drive, and NIC. With dual-peer
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PCI buses, each bus can provide peek bandwidth in parallel with the other controller, allowing
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an aggregate I/O bandwidth of 267MB/second. This implementation provides twice the
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bandwidth of single bus architectures. Also, dual PCI buses allow key peripherals to be
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connected to separate buses to balance overall system throughput. The dual PCI buses also allow
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for greater system I/O integration and expandability by supporting up to 12 PCI devices which is
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twice the number supported on single bus implementations. This allows the Compaq
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Professional Workstation 6000 to deliver six PCI-based I/O expansion slots while also
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integrating other PCI components such as the SCSI and network controllers on the system board.
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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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Workstation 6000 is able to deliver optimized multiprocessing support. The Intel Pentium II
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processor enables multiprocessor support by including circuitry in the processor that determines
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how multiple processors can share the CPU bus. However, most multiprocessing
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implementations in the Intel based Windows NT workstation market take advantage of this
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support by simply adding an additional processor to an already existing desktop design. Compaq
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takes multiprocessing to the next step with the Compaq Highly Parallel System Architecture by
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. . enhancing memory and I/O bandwidth as well. Multiprocessor Systems designed without the
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Compaq Highly Parallel System Architecture will quickly encounter a bottleneck as the multiple
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. . processors try to access the other system resources, such as memory and I/O subsystems, that
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have not been enhanced to accommodate the additional data traffic. The Compaq Highly Parallel
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System Architecture significantly reduces these bottlenecks by incorporating enhanced
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subsystem resources, such as dual memory controllers and dual- peer PCI buses, to accommodate
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the increased data traffic from the multiple CPUs.
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Compaq Workstations - Key Technologies
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