Path: utzoo!attcan!uunet!snorkelwacker!think!redsox!campbell From: campbell@redsox.bsw.com (Larry Campbell) Newsgroups: comp.unix.i386 Subject: Re: SCSI and 386/ix Message-ID: <1535@redsox.bsw.com> Date: 8 Feb 90 03:46:36 GMT References: <25c1fdd8:490comp.unix.i386@nstar.UUCP> <1990Feb3.191842.1991@ddsw1.MCS.COM> Reply-To: campbell@redsox.UUCP (Larry Campbell) Organization: The Boston Software Works, Inc. Lines: 18 In article pcg@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@redsox.bsw.com 120 Fulton Street wjh12!redsox!campbell Boston, MA 02109