There are two dominant interface types between the hard disk drive and the motherboard: EIDE and SCSI. The earlier IDE interface evolved from the PC industry while SCSI was a product of the workstation and server industry. Today, both are available. In the past, SCSI performance and cost were both significantly greater than IDE. But the EIDE standard closed the performance gap a few years ago, while the price difference still exists. Perhaps equally important is that many motherboards now include EIDE interfaces as integral components so that no separate control card is required to be purchased or to take up a PCI socket. SCSI drive capacities can run a little higher than IDE drives which may be important for some installations. Several different SCSI standards exist, including Wide, UltraWide, SCSI-2 and SCSI-3. Systems are usually downwards compatible, but it is safest to match the drive's capabilities with that of your SCSI controller. Beowulf-class systems have been implemented with both types and your needs or preferences should dictate your choice. The authors have continued to rely on EIDE drives due to their lower cost.
The primary performance characteristic of a hard drive is its capacity. EIDE hard drives with 17 GByte capacities are available for under $300 and 1GByte drives cost below $100. Also of interest is the rotation speed, measured in revolutions per minute (rpm), which governs how quickly data can be accessed. The fastest rotation speeds are found on SCSI drives, and are now around 10000rpm.
3.7 PCI Bus
While the PC motherboard determines many of the attributes of the PC node, it also provides a means for user defined configuration through the Peripheral Component Interconnect or PCI bus. This interface is incorporated as part of virtually every modern motherboard providing a widely recognized standard for designing separate functional units. PCI is replacing the ISA and EISA buses as the principal means of adding peripherals to personal computers.
The PCI standard permits rapid data transfer of 132 MBytes per second peak using a 33 MHz clock and 32 bit data path. A 64 bit extension is defined enabling peak throughput of 264 MBytes per second when used. A further advance, sometimes referred to as PCI-2, will permit bus clock rates of 66 MHz for a peak transfer bandwidth of 528 MBytes per second.
The PCI bus permits direct interconnection between any pair of PCI devices, between a PCI device and the system memory, or between the system processor and the PCI devices. PCI supports multiple bus masters allowing any PCI device to take
