RANA Systems Elite Controller, Руководство пользователя

Страница: 312 / 328

ELITE SERIES USER MANUAL APPEN. A - DISK I/O
A . 7 . S e c t o r I n t e r l e a v i n g
This process involves staggering sectors on a
track to improve access times. There is usually
a delay between reading or writing one sector
and reading or writing the next sector. This
delay usually depends on the user’s program and
can vary greatly.
If sectors are stored in numerically ascending
order, it may take a full revolution of the
diskette before the next sector can be accessed
(unless the application was extremely fast).
Rearranging the sectors into a different order
(interleaving) speeds up accessing.
On DOS 3.2.1 and earlier versions, the 13 sec-
tors are physically interleaved on the diskette.
Since DOS is booted from ascending sequential
sectors and files are generally stored in de-
scending sector order, no single interleaving
technique works well for both booting and se-
quentially accessing a file.
To maximize performance in DOS 3.3, the inter-
leaving is done in the software. The 16 sectors
are placed on the diskette in numerically
ascending order and are not physically inter-
leaved. A table is used to translate the phys-
ical sector number into a soft sector number
used by DOS.
P a g e A - 4 1