format table of CDC 9720-850

[Greg Wageman]

In article <2682 at brazos.Rice.edu> jesse at tcgould.tn.cornell.edu (Jesse Lee) writes:
>X-Sun-Spots-Digest: Volume 8, Issue 181, message 12 of 15
>
>We have problem of formatting a CDC 9720-850 disk on a Sun 3/260 running
>SunOS 4.0.3. We always get the error:
>
>Hard sectors less than nsects
>
>We begin to wonder if the entry of CDC 9720-850 in the file
>/etc/format.dat is correct.  Here is the entry found in that file:
>
>disk_type = "CDC 9720-850" \
>	: ctlr = XD7053 \
>	: ncyl = 1358 : acyl = 2 : pcyl = 1360 : nhead = 15 : nsect = 66 \
>	: rpm = 3600 : bpt = 41088 : bps = 610

My CDC manual lists an 850 as having 1381 logical cylinders, 15 heads and
41,088 bytes per track.  The Sun entry is going to short you some 21
cylinders of space.

However, the real issue in the error message is the number of data
sectors/track.  This is configurable, and depends on the setting of a bank
of switches on the drive, in addition to the runt-sector enable jumper (if
present).  You will have to consult the drive manual, as there are 3
different types of boards with different settings possible for each.
Sun's entry of 66 sectors/track is a reasonable number; note however that
with 610 bytes/sector (as set by the above-mentioned switches), 41,088/610
= 67 and a runt, so Sun is allowing for sector slipping.

The important thing is that the drive switch configuration match the
number of bytes per sector that the controller is expecting. 

Copyright 1989 Greg Wageman	DOMAIN: greg at sj.ate.slb.com
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