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HP 9895A Disc Memory Command Set A-49
If the type parameter is set to 2, the disc will be given HP
format. Double-sided discs will automatically be forl1"atted
on both sides, and single-sided disc only on head O. If the
type parameter is set to 8, the disc will be formatted IBM.
Double-sided discs are not supported in IBM format.
Single-sided discs will be formatted on head 0 only (IBM
standard). Other values of type will cause an 1/ 0 program
error.
The interleave parameter determines the order in which
the sectors occur on a track. Data transfers which use the
internal buffer on the 9895A, or host systems that accept
data slower than the disc rate, operate more efficiently if
the ordering of the sectors is non-sequential. Non-
sequential sectors ordering allows for sectors to be ar-
ranged on the disc by logical use instead of by physical
location.
In general, the interleave parameter indicates the number
of disc revolutions required to send or receive one track's
worth of data. For example, an interleave value of 5 would
indicate that the sectors would be arranged on the disc in a
manner that would require five revolutions to read one
track.
NOTE
An interleave parameter value of 2 (two revolutions per track)
generates the sector sequence with the minimum time required to
transfer one track.
HP format also uses the interleave parameter to determine
the inter-track spiral offset. This offset minimizes the effect
of track-to-track seeks by physically arranging sector 29 of
one track and sector 0 of the next to make the track seek
time approximately the same as the rotational latency.
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