To summarize the differences between these three related feature sets:
- Ultra3 SCSI: At least one, and as many
as five, of the main SPI-3 features.
- Ultra160(/m) SCSI: Fast-80 signaling,
CRC and domain validation are mandatory; QAS and packetization optional.
- Ultra160+ SCSI: All five features are mandatory.
Aside from these definitional differences, all these terms refer to the same basic
interface. See the discussion of the SPI-3 standard and
the items below for more details.
Defining Standard: SCSI-3 / SPI-3.
Special Features: Ultra3 SCSI devices include support for all of the
following five SPI-3 features:
Bus Width: Wide (16-bit). Narrow mode is not supported.
Signaling Method: LVD only. (Multimode drives may optionally run in SE
mode, but throughput will drop to Fast-20 (Ultra) levels.)
Signaling Speed and Bus Throughput: 40 MHz bus speed; 160 MB/s.
Number of Devices Supported: 16 for cables up to 12m in length; 2 for
cables over 12m.
Termination: LVD termination.
Cabling and Maximum Cable Length: "P" cable (68 pins).
Maximum of 25m if no more than 2 devices are used, otherwise 12m.
Next: Ultra320 SCSI
