Storage Networking Architectures
Network Metrics
Parallel Bus Basics
(applies to Parallel SCSI, ATA/IDE etc)
• Skew effect:
– Small differences between conductors/connectors
cause bits to move at slightly different speeds
– Receiver cannot reconstruct original data if the signal
is too skewed
– Limits transmission distance of parallel bus
Computer buses, both internal (e.g. PCI) and external (e.g. SCSI) have to deal
with a particular problem:
They have to keep the data bits across the connectors in line so that
they all arrive together, within a very tight time period.
The further the information moves down a parallel bus the more the
minute differences between individual connections come into play and
the original data starts to scatter (skew), becoming corrupt and
unusable.
This skew effect limits the distance over which high speed, parallel bus
connections can be used.