WD1006 Controller on 386/ix

[James Van Artsdalen]

IN article <865 at altger.UUCP>, dirk at altger.UUCP (dirk) wrote:
> Does anybody out there have any suggestion how to use
> the WD1006 (RLL, 1:1) Controller under 386/ix or 386/V ?

The WD1006 also comes in a non-RLL ST506 configuration, and was/is
available with or without the floppy interface on board.

> I found out that Interleave 6 is the fastest one, but it is
> slower than using a regular WD1003 with interleave 2.

This makes little sense to me: this is a *1:1 interleave* controller:
you should use 1:1 interleave.  If the controller buffers by reading
an entire track at a time, formatting with 6:1 interleave could really
slow things down if the controller isn't smart enough to read the
sectors as they come (and I think the WD1006 might be this dumb - if
not, then your chosen interleave would be entirely irrelevant).

> So why does MS-DOS increase disktransfers by 3 when using
> the 1:1 interleave but 386/ix slows down rapidly ?

Well, in theory, a sufficiently fragmented file system with a
sufficiently fast drive *might* see this effect.  If memory serves me,
the rotational time of a most hard disks is 17ms.  If you read an
entire track, but really only wanted one sector, the wasted time is
8.5ms.  That's a lot of time for something like the CDC Wren III.

However, if a file system gets this badly fragmented, it should
probably be cleaned up for speed.  In particular, I re-load my
/usr/local directory regularly so that emacs and other binaries are
kept unfragmented for quick loading by my 1:1 controller (WD1007/WA2).
-- 
James R. Van Artsdalen   ...!ut-sally!utastro!bigtex!james   "Live Free or Die"
Home: 512-346-2444 Work: 328-0282; 110 Wild Basin Rd. Ste #230, Austin TX 78746