This message is from the T13 list server.
On Thu, 21 Mar 2002 09:11:51 -0800, Marushak, Nathan wrote: >This message is from the T13 list server. >As mentioned in the previous email, obsoleting commands makes the dialog >between the host and drive more difficult. Maybe but probaby not. Even though the RECALIBRATE and FORMAT TRACK commands are obsolete I am sure most drives still implement these commands (don't reject the commands as invalid) but the drive probably implements the command as a NO-OP. >Is it possible that for these >obsoleted commands a drive vendor may return an error? Legally they could. But no drive manufacturer is going to cause themselves a bunch of problems by outright rejecting some of these old commands. Accepting the command and performing no operation is a much better way to go. >If so, you have now >required all host drivers to change their code to stop using these commands. >At a minimum, they may need to be aware that the command may not succeed and >appropriately ignore the possible error. It seems to me this leaves a lot >of room for ambiguity. Welcome to the real world. The real world is a messy place. >If everybody only ever had to worry about the most current incantation of >the spec, then obsoleting pieces of the spec isn't such a concern. The >problem is that people always have legacy requirements. The problem with R/W LONG is very similar to the current problem with the AV commands: There was (is) no single implementation. As long ago as 1990 there were widely different implementations of R/W LONG. Since the function performed by these commands was becomming less and less important no one wanted to try to solve this variable implementation problem in an ATA-x standard. So the commands became first "vendor specific" and then "obsolete". That process required several years. As for the current AV commands... One possible outcome will be that the AV command codes will be "reserved for the obsolete AV feature". This is one way for T13 to address the issue that the command codes are being used but there is no common/standard implementation (especially if the DVR market never develops). Yea, it is too bad things work that way but the real world is a messy place! *** Hale Landis *** www.ata-atapi.com ***
