12 Jan
1999
12 Jan
'99
4:10 p.m.
On Tue, 12 Jan 1999, Fred Cisin (XenoSoft) wrote:
When going to the directory on a system without a
track 0 stop or track
0 switch, it DOES substantially reduce the average access.
But, if there IS a track 0 stop, or track 0 switch, then it is normally
possible to get to track 0 at full maximum velocity, rather than stepping
one track at a time, pausing (and maybe reading) before taking the next step.
That usually makes even the maximum seek to track 0 take even less than
half the time that track by track stepping would.
I don't know if this makes complete sense on the Apple disk drives. When
you wanted to step, say, 5 tracks over, you massaged the stepper motor the
requisite number of times to get it to where you assumed it would be 5
tracks over. Then the DOS went about its business reading for the sector
it was looking for. If it didn't find it then it assumed a problem and
recalibrated (to track 0), then stepped back the requisite number of times
to get to the track you originally were headed for. This scheme resulted
in 99.99999% success in jumping from track to track. And the CATALOG
track was 17 (on a 34 track formatted disk).
Sellam Alternate e-mail: dastar(a)siconic.com
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