HP Vectra XU 6/XXX HP Vectra XU 6/XXX - Guide to Optimization Performance - Page 19
Increasing The Speed Limit With Ultra Scsi
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If you need to install an accessory board in your PC, HP recommends that the PCI bus is your first choice for expansion. PCI Plug and Play The PCI standard supports Plug and Play, which means easy configuration for installed peripherals. If you install an extra PCI accessory board, the board will be configured for use automatically. Low Power Migration The PCI bus in your PC supports PCI accessory boards that use two different power sources, 3.3 volts or 5 volts. Most currently available PCI accessory boards use the 5 volt power source. Accessory boards that use the 3.3 volt power source use less power, which helps to reduce the overall power consumption of your PC. As more 3.3 volt PCI accessory boards become available, you will be able to install these inside your PC immediately. PCI Clock Speeds The PCI bus in your PC uses a clock that is half the speed of your processor's local bus. This means that your PCI bus uses a clock of either 30 MHz or 33 MHz, depending on your processor. At 30 MHz, the PCI bus can transfer up to 120 MB of data each second, while at 33 MHz, the transfer rate is 132 MB each second. INCREASING THE SPEED LIMIT WITH ULTRA SCSI Your HP Vectra XU PC integrates an advanced SCSI controller for connecting mass storage devices. This SCSI controller provides a high-capability SCSI channel with two connections: one on your PC's system board for connecting internal SCSI devices; and one on your PC's rear panel for connecting external SCSI devices. SCSI Interface Standards The Small Computer System Interface (SCSI) standard offers the highest level of peripheral connectivity available to a PC. The SCSI channel in your PC can connect up to seven mass storage devices, both internal and external. Up to five of these devices can be installed inside your PC. The SCSI standard is highly flexible, enabling devices of different types and capabilities to be connected on the same channel. Communication between the SCSI controller and a SCSI device is based on a request-acknowledge protocol ("handshaking"), with each device (including the controller) having a SCSI address for identification.