Date : Wed, 23 May 1990 03:00:16 EDT
From : dg%pallio.UUCP@XAIT.Xerox.COM (David Goodenough)
Subject: floppy drive hardware
mcsun!unido!balu!tilmann%cosmo.UUCP@uunet.uu.net (Tilmann Reh) says:
> Last (not least), I have to mention that the 765 FDC is better than the WD
> controllers. It does handle four drives without software overhead,
So does the 1793. At least the 1793 in my Televideo 803 seems to talk quite
happily to all four drives attached.
> and the
> interfaces to both CPU and FDC are very simple. The software expense for
> getting things working is smaller,
Here I have to disagree. I've worked with both the 1793, and the 765, and the
software overhead for the 765 is way higher than that for the 1793.
> as you don't have to fool around with
> the bits on disk (when formatting, for example)...
Fooling with the bits _DOES_ have it's advantages :-)
I've been reading the discussion about just how much you can actually fit
on a DS DD disk with various controllers with quite a grin. With a 1793
is _IS_ possible to get the equivalent of 11 * 512 byte sectors on one
track, in tests I've had it working. You put 5 * 1K (10 * 512), plus a
single 512 byte sector in the space left over. One of the nice things
about the 1793 is that you can get right inside it's mind: a read track
operation just sits there and reads _EVERYTHING_ - gaps, address headers,
data, CRC bytes, the works. [1] So you put 5 * 1k on there, do a read track,
and find about 680 to 700 bytes left over: plenty of space for a 512 byte
sector to snuggle into.
[1] this also makes it infinitely superior for doing error recovery - a
read track _CAN'T_ bitch about bad CRC's since it ignores them.
> Fine chip, better than every WD x79x !
I'll agree with that when I see it put 440K on a DS DD floppy.
--
dg@pallio.UUCP - David Goodenough +---+
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