Slide 3 of 33
Notes:
Narrow = 8 bit data path, Wide = 16 bit data path, SSA = 1 bit data path
Single Ended = TTL-style signal references; i.e., +5V = 1 and 0V = 0 with ground potential being zero volts.
Differential = pair of signals compared to each other. If one wire’s voltage is higher than the other it is considered a 1. The reverse condition is considered a 0. Differential is much more reliable than single ended in terms of high speed signal integrity.
LVD = Low Voltage Differential. A new spin on differential technology that does not require separate high powered bus transceivers as with standard differential SCSI. LVD devices can be compatible with single ended SCSI devices.
“normal” = 5MHz, Fast=10MHz, Ultra=20MHz, Ultra2=40MHz, Ultra3=80MHz. Combined with a narrow bus, the MHz translates to MB/sec. Combined with a wide bus the MHz translates to 10, 20, 40, 80 and 160MB/sec, respectively. As an aside, note that only during data transfers does the SCSI bus ever achieve these rates.
SCSI-1 is the original standard. It had a number of holes in the specification, so SCSI-2 came about to correct those holes. SCSI-2 included synchronous and fast specifications. SCSI-3 describes serial SCSI protocols, etc., as is now implemented in SSA and FibreChannel.
