format table of CDC 9720-850

[chomolungma!poffen at uunet.uu.net]

In article <2905 at brazos.Rice.edu> greg at sj.ate.slb.com (Greg Wageman) writes:
>X-Sun-Spots-Digest: Volume 8, Issue 191, message 7 of 9
>
>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.

Be careful with the settings. Sun's format program REQUIRES an extra
sector for sector slipping when using an XY753 (XY7053 or SMD-4). This
mean that you should pick the number of sectors that best fits (more than
600, the XY753 requires 88 bytes of overhead minimum per sector, and only
supports 512 byte sectors) You should set up the drive to use runt
sectors, and use the round down method given in the CDC manual. Once you
pick the number of sectors on the drive, tell format to use 1 LESS than
this. However the bps entry should indicate the bytes/sector found in the
table and the bpt entry should be the TOTAL bytes per track (including
runt sectors).

Here is what I use and is probably the most optimum, this uses fixed clock
(not byte clock).

disk_type = "CDC 9720-850" \
        : ctlr = XD7053 \
        : ncyl = 1379 : acyl = 2 : pcyl = 1381 : nhead = 15 : nsect = 67 \
        : rpm = 3600 : bpt = 41088 : bps = 603

This means the drive must be set to 68 sectors on its switches.

e-mail me for switch settings if you need it.


Russ Poffenberger               DOMAIN: poffen at sj.ate.slb.com
Schlumberger Technologies       UUCP:   {uunet,decwrl,amdahl}!sjsca4!poffen
1601 Technology Drive		CIS:	72401,276
San Jose, Ca. 95110
(408)437-5254