hard-sector 5 1/4 disk

From: Sellam Ismail <foo_at_siconic.com>
Date: Tue Oct 30 22:35:03 2001

On Tue, 30 Oct 2001, Richard Erlacher wrote:

> I have to disagree, actually, because the Apple diskettes all seem to
> have the holes, not that it matters. While the drive may not have the

Only because that's how they were manufactured. It would be silly to
order disks without the index holes at what most likely would have been a
much higher price just because you didn't need it.

> Which, admittedly, I don't understand, since the PROM they used was
> rather small. (...that's where the firmware lives, doncha know...)
> Most of the work was in the software, actually, since it had to do
> what the disk format required, and figure out along the way which one
> it was.

The PROM only had the boot code in it (less than 256 bytes...some of the
tightest code EVER!) It was responsible for loading the first sector of
the first track into memory and then executing that code. It could be
actually be used to read any numbre of sectors from the track the head was
currently positioned over. With the addition of maybe 32 more bytes of
6502 code, you could write a head positioner routine that could move the
head around and read any sector from the disk.

> I've never liked Apple-disk-related problems, since the Apple system
> was incredibly fragile and highly unreliable. The first Apple client


> I had who had been using an Apple][+ in his business summarily took
> his ][+, drives, and monitor, the whole shebang, out to his dumpster
> the day I moved his database to a CP/M system with a conventional FDC
> and a conventional pair of 8" DSDD drives. I'd say he was in hog
> heaven. His business picked up (though I don't know that the switch
> had anything to do with that) and his monthly expenditure for MAALOX,
> Whiskey, and prune juice was substantially reduced. Moreover, he got
> to see a lot more of his wife and kids.

Sounds like user error to me. RTFM.

> Until a few weeks back when I got into retrieving old 6502 source
> files, I had forgotten what a piece of crap that disk subsystem was.


> No wondern so many folks switched to 8" drives. I surely wish I could
> find an old SVA controller ... <sigh> It's a real wonder
> microcomputers caught on as well as they did, given the standard set
> by the Apple ][. The work WOZ did to create the disk subsystem was
> really ingenious, but still orders of magnitude less reliable than
> what was offered on more conventional systems.

I have hundreds (>~500) Apple ][ disks that are still readable to this
day. Of my 17 or so years of hacking Apple ][s, I've only lost a handful
of disks, and that was usually due to physical errors. Once or twice I
lost a disk because random sectors were overwritten whilst hacking and the
system jumped into the middle of a DOS call, but that was rare.

Anyway, I'll just take your statement for what it is.

Sellam Ismail Vintage Computer Festival
International Man of Intrigue and Danger http://www.vintage.org
Received on Tue Oct 30 2001 - 22:35:03 GMT

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