Late letter ballot comment on SAT-3

Neil Wanamaker Neil.Wanamaker at pmcs.com
Thu May 9 13:00:12 PDT 2013


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Mark,
My attention has been called to Table 197 of ACS-3, which says in part:
If State is set to 0001h, then the SET FEATURES command (see 7.45) shall
determine the
state of the write cache (see 7.45.7).
If State is set to 0002h, then write cache shall be enabled.
If State is set to 0003h, then write cache shall be disabled.
If State is set to 0002h or 0003h, then write cache shall be set to the
specified state, and
any attempt to change the write cache settings using a SET FEATURES command
shall
not result in an error and shall not change the operational state of the
write cache.
In all cases, the VOLATILE WRITE CACHE ENABLED bit (see A.11.6.2.4) shall
reflect the current
operational state of write cache (i.e., if set to one, then volatile write
cache is enabled, and
if cleared to zero, then write cache is disabled).
The default is State set to 0001h.
This suggests to me that table 191 of SAT-3, under the section on WCE, there
should, at a minimum, be a reference to this, or even better, indicate that
if the drive supports SCT FEATURE Control, that that be the mechanism for
setting the state of the write cache.
Neil Wanamaker
Principal Engineer, Enterprise Storage Division
PMC-Sierra
1380 Bordeaux Dr., Sunnyvale, CA 94089
408.239.8277
neil.wanamaker at pmcs.com



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