Fea tu re D es cri pt io ns
Maxtor Atlas 10K III 6-11
With Ultra160 and Ulra3 20 SCSI int erfaces, Maxtor has int roduced a new method of
clocking data on the SCSI bus. This method, called D ouble Trans ition (DT) c locking,
uses both t he r isi ng and falling edges of the REQ and AC K sign als to cl oc k da ta int o
the receiving device. This has the advantage of allowing the REQ and ACK signals
to run at half the frequency that would be required under the traditional Single
Transiti on (ST) SCSI clocking scheme for the same data rate. Lower frequency clocks
result in a more reliable bus. Figure 6-1 illustrates the difference between DT and ST
clocking.
ST and DT CLo cking
The Maxtor Atlas 1 0K III dis k dr ive c an operate at s peeds up to 80 MB/sec in either
ST or DT modes, depending on the capabiliti es of the host adapter. Transfer rates
above 80 MB/sec are only supported in DT mode, as required by the SPI-3 SCSI
standard.