RANA Systems Elite Controller, User Manual

Page: 313 / 328

ELITE SERIES USER MANUAL APPEN. A - DISK I/O
For example, if the sector number found on a
disk were a 2, this is used as an offset into a
table where the number $0B is found. Thus DOS
treats the physical sector 2 as sector 11 ($0B),
presenting no problem If RWTS is used for disk
access.
To eliminate access differences between reading
and booting files, DOS is actually loaded back-
wards into memory in descending sequential order
during booting, just as files are accessed.
Thus, one interleaving cuts disk access time.
DOS, CP/M, and Pascal diskettes all use software
interleaving though each uses a different sector
order. The figure below gives the standard in-
terleave tables for each operating system.
For the dual headed Elite Two and Three drives,
the sector interleaving tables within the
Rana enhanced operating systems are extended to
a full 32 sectors. This is due to the fact that
the enhanced operating systems treat each
cylinder as a single track, with sectors 0-15 on
the first side (or first true track) and sectors
16—31 on the second side (or second true track).
Due to the way in which the Rana dual headed
diskette formatting utilities operate, it is not
sensible to interleave sectors between the two
sides of the diskette. Therefore the sectors on
the first side are interleaved with themselves,
and the sectors on the second side are inter-
leaved with themselves.
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