SCSI and 386/ix

Larry Campbell campbell at redsox.bsw.com
Thu Feb 8 14:46:36 AEST 1990


In article <PCG.90Feb5190711 at rupert.cs.aber.ac.uk> pcg at rupert.cs.aber.ac.uk (Piercarlo Grandi) writes:
-This perplexes me. You sure that a WD1003 style controller can
-overlap seeks? Are there any that do? I can hardly imagine seeks
-not being synchronous to the controller with a WD1003 style
-controller, that must issue step pulses to the head.
-
-Are there really any RLL or MFM controllers (the WD1006 is by
-your implication) that can step independently the two arms?

Not exactly, but:  most RLL/MFM drives are "buffered seek" drives.  This
means that the step pulses do not have to be issued at a rate that matches
the physical movement of the head, but can be issued all at once (50 usec
apart, I seem to recall);  the drive counts them and then steps the heads
itself.  So I think you could fake overlapped seeks with such a drive.
-- 
Larry Campbell                          The Boston Software Works, Inc.
campbell at redsox.bsw.com                 120 Fulton Street
wjh12!redsox!campbell                   Boston, MA 02109



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