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From: seeger@beach.cis.ufl.edu (Charles Seeger)
Newsgroups: comp.unix.xenix,comp.unix.microport
Subject: Re: WD1006 Controller on 386/ix
Keywords: controller, interleave, WD1006
Message-ID: <16745@uflorida.cis.ufl.EDU>
Date: 26 Jul 88 03:17:15 GMT
References: <865@altger.UUCP>
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Reply-To: seeger@beach.cis.ufl.edu (F.L. Charles Seeger III)
Organization: UF EE Department
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Since the WD1006 has a full track cache, interleaves other than 1:1 don't
really affect the transfer rate off the disk, i.e. it takes only one disk
revolution to read the whole track.  Thereafter, interleaved reads should
progress at the same rate regardless of the interleave factor.  At that
point, reads should only be limited by system hardware and software.  Note
that the 1006 has 70 ns ram on board, so it's pretty fast.  Have you
disabled the cache?  I don't remember if that's even possible, not having
the docs here.

My experience using these controllers (WD1003, WD1006) has been with the
RLL versions under (ugh!) DOS.  Never tried anything other than 1:1 on the
1006 (in a 20 MHz '386), but the 1003 peaked at 3:1 (both the same '386
and a 10 MHz '286).  Keep in mind that the 1.5x increase in transfer
rate for RLL probably accounts for the discrepency in interleave factor
on the 1003 (your 2:1 vs. my 3:1), with the net transfer rate being
about the same.

Still, I don't understand the 6:1 interleave being optimum for your
1006.  How strong an effect was the interleave factor?

Chuck
(someday I'll create a neat ~/.signature)