CDC Read Ahead Buffer

[neese at adaptex.UUCP]

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!neese