<
hardware> (Or "host
adaptor") A device that communicates
between a computer and its
SCSI peripherals. The
SCSI
adaptor is usually assigned
SCSI ID 7. It is often a
separate card that is connected to the computer's
bus
(e.g.
PCI,
ISA,
PCMCIA) though increasinly,
SCSI
adaptors are built in to the
motherboard. Apart from being
cheaper, busses like PCI are too slow to keep up with the
newer
SCSI standards like
Ultra SCSI and
Ultra-Wide SCSI.
There are several varieties of
SCSI (and their connectors) and
an
adaptor will not support them all.
The performance of
SCSI devices is limited by the speed of the
SCSI adaptor and its connection to the computer. An
adaptor
that plugs into a parallel port is unlikely to be as fast as
one incorporated into a motherboard. Fast adaptors use
DMA
or
bus mastering.
Some
SCSI adaptors include a
BIOS to allow PCs to
boot
from a
SCSI hard disk, if their own BIOS supports it.
Adaptec make the majority of
SCSI chipsets and many of the
best-selling adaptors.
Note that it is not a "
SCSI controller" - it does not control
the devices, and "
SCSI interface" is redundant - the "I" of
"
SCSI" stands for "interface".
(1999-11-24)