Format.dat for CDC9720-1230?

[Russ Poffenberger]

In article <9892 at brazos.Rice.edu> xait!mgb at cs.utexas.edu (Michael G. Burner) writes:
>
>disk_type = "CDC 9720-1230" \
>        : ctlr = XD7053 \
>        : ncyl = 1633 : acyl = 2 : pcyl = 1635 : nhead = 15 : nsect = 83 \
>        : rpm = 3600 : bpt = 50400 : bps = 600

This will not work correctly. The 7053 requires an extra sector configured
on the drive for slip sectoring. This implies that the drive would have to
be set for 84 sectors. At 84 sectors, a 9720-1230 has exactly 600 bytes
per sector.  Since the 7053 uses 512 byte sectors with a minimum of 88
bytes overhead, plus 4 bytes minimum for the runt sector, this adds up to
at least 604 bytes per sector required. This means that the next setting
of 83 sectors on the drive (606 bytes per sector) and 82 set in the
format.dat parameters is the correct setting.

Russ Poffenberger               DOMAIN: poffen at sj.ate.slb.com
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