neese@adaptex.UUCP (07/15/89)
I have seen enough on the net about this so I thought I would make it a global
posting as opposed to a reply.
The CDC Wren series SCSI drives all come preformatted at 1:1 interleave
by default. The CDC Wren IV and above have read ahead capability, but it is
turned off by default, unless you buy the drive from Tandy. Tandy is the
only distributor of the CDC drives that has the read ahead turned on by
default from CDC.
The read ahead buffer can be enabled via the SCSI mode sense/select
commands for these drives. The mode page is 38H and the location in the
page is byte 2 bit 4. Of course the header of the page is 14 bytes
long so the actual byte location is byte 15. The page length is 14
bytes.
I have writen an extensive piece of software for bit fiddling all the
mode pages of a SCSI device. It also includes a low level formatter.
It does run under MS-DOS and uses menus for poking around in a SCSI
device. It was designed to run on the AHA-154x/1640 family of SCSI
host adapters from Adaptec. If you are interested, please send E-mail.
Roy Neese
Adaptec Central Field Applications Engineer
UUCP @ {texbell,killer}!cpe!adaptex!neese
merch!cpe!adaptex!neesebote@csense.UUCP (John Boteler) (07/19/89)
From article <7100007@adaptex>, by neese@adaptex.UUCP: > > The CDC Wren IV and above have read ahead capability, but it is > turned off by default, ... > The read ahead buffer can be enabled via the SCSI mode sense/select > commands for these drives. The mode page is 38H and the location in the > page is byte 2 bit 4. Of course the header of the page is 14 bytes > long so the actual byte location is byte 15. The page length is 14 > bytes. I'm lost. > I have writen an extensive piece of software for bit fiddling all the > mode pages of a SCSI device. It also includes a low level formatter. > It does run under MS-DOS and uses menus for poking around in a SCSI > device. Must these command sequences be issued each time the device is acessed? Powered up? Only once in its life? I am not intimately familiar with the SCSI spec., so perhaps pointers to references or a brief discussion would clear up much of the confusion seen here. Thanx in advance. -- Bote uunet!cyclops!csense!bote {mimsy,sundc}!{prometheus,hqda-ai}!media!cyclops!csense!bote
neese@adaptex.UUCP (07/22/89)
>> STUFF DELETED < >> I have writen an extensive piece of software for bit fiddling all the >> mode pages of a SCSI device. It also includes a low level formatter. >> It does run under MS-DOS and uses menus for poking around in a SCSI >> device. > >Must these command sequences be issued each time the device is acessed? >Powered up? Only once in its life? There are two options in the saving of a mode page. Either permanently or save until the next SCSI bus reset/power cycle. >I am not intimately familiar with the SCSI spec., so perhaps >pointers to references or a brief discussion would clear >up much of the confusion seen here. Okay. Roy Neese Adaptec Central Field Applications Engineer UUCP @ {merch,texbell,killer}!cpe!adaptex!neese