RQDX3 software interleave

Jason T. Miller jasomill at shaffstall.com
Thu Jun 8 06:07:58 AEST 2000

> Yes, the RQDX3 is supposed to do this for you so you don't have to deal
> with it, ...
I guess I should have sat down and thought about it, I never even
considered the hardware doing software interleave (quite a dumb thing to
do, IMHO, unless you want to sell preformatted diskettes for use in
systems with widely varying performance characteristics; who would want to
do that :). Thanks, Herr Ivie, for that insight. Also thanks to SMS for
the disklabel enlightenment. I should have a workable solution soon,
though doing the interleave code in 4.4BSD kernelland doesn't seem like
much fun and would reduce the general applicability of the driver (I'd
like to see what the FreeBSD committers would think when I suggest
_that_!); I think I'll just write an "interleave filter" in userland and
leave it at that.

> What sort of info are you looking for? Floppy drivers are a PITA to
> and you should be happy the RQDX3 is hiding it from you.
Don't get me wrong, I _am_ happy. I like smart hardware as long as it
doesn't try to second-guess me; I'm a big fan of SCSI. Just a natural
and (usually, but not always) healty curiousity. And I know how much
fun floppy drivers are to write; one of the products developed by my
employer (though before I was thus employed) was a disk conversion system.
And we even used one of the more "intelligent" floppy controllers, an
experimental TI 9909 that handled "pretty much everything" for you (as
long as "pretty much everything" involved writing single-density IBM 8"
diskettes -- reminds me of the line in Raising Arizona, when N. Cage asks
the cashier if he has balloons in funny shapes and he replies: "if you
think a circle is a funny shape"). So I have the source code to a floppy
driver that handles almost any disk type imaginable (as long as the
data rate isn't too high: 2.88MB disks zum beispiel), all written in
assembler and PLM for an 8085; talk about tight code. Speaking of PITA
device control, wasn't it the DEC RX02 that wrote address information in
single density and data in DD?

Once again, thanks for everyone for all the help. I'll have this thing
working soon.


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