3 Nov
2024
3 Nov
'24
6:10 p.m.
Non-descript 5.25 DS/DD (they don't format as 1.2M disk using a 1.2 5.25"
drive, so I'm pretty sure they are actual 360KB disks). That said, I
haven't really fully confirmed if it's a 1.2M drive. TEAC FD-55GFR
142-U, because I haven't actually come across any 1.2M formatted media.
I've wondered if maybe one of the heads on the D: drive the Sharp PC-5000's
dual disk drive might have some kind of issue (either the REad or Write
head, not sure which) - just since it seemed more likely to end up with
some bad sectors marked when using FORMAT.COM (whereas on other systems,
the same disk would format fine with no bad sectors).
-Steve
On Thu, Oct 31, 2024 at 7:17 AM osi.superboard via cctalk <
cctalk(a)classiccmp.org> wrote:
Steve,
could you please explain, what exact disk media you are using.
On 30.10.2024 05:03, Steve Lewis via cctalk wrote:
Fascinating notes!
I did run into oddities when using a 360KB disks in between a 1.2M 5.25
drive on the '386 and the 5.25 drive on the Sharp PC-5000. I forget my
exact sequence of events, but in short the MS-DOS 2.00 FORMAT.COM on the
Sharp PC-5000 would start marking a few bad sectors (sometimes just a few
KB, sometimes as much as 20KB of bad sectors). And yet those same disks
were formatted as just fine and no bad sectors over the '386. Or, if I
used IMD and wrote full MS-DOS 2.00 image to the disk, then the disk
would
work (and boot) fine in the Sharp PC-5000.
Without nit-picking the
specifics here (of whatever I did) - my lesson was there is definitely a
difference between a completely uninitialized disks, versus something
that
has been previously formatted. Which, yeah, duh
- but my real lesson
was:
you can't always FORMAT.COM your way back
into a bootable disk. If
something else has "touched" the boot sectors, then another system might
start flagging those as bad sectors.
I'm not sure if IMD (ImageDisk) trumps all that? Meaning, whatever crap
is
on the disk, does IMD not care? In otherwords,
is using IMD kinda-sorta
like degaussing (and then applying whatever the image is)? It just
seemed
to me that however I mangled the format on a
disk, IMD was always able to
get me back into a usable (and bootable) disk.
I do remember (vaguely for me) in the 80s we'd get boxes of uninitialized
disks, and there were generally warnings along the lines of once it was
formatted to whatever system you intended to use the disk for, it was
thereafter basically committed to being used for that system. (but it
seems only because, back in those days we didn't typically have the
benefit
of something like IMD software or a Greazeweasal
- and I imagine the
documentation from disk vendors didn't want to get into the weeds of
waving
magnets around your disk, especially when they
already had bold warnings
of
keeping your disk the heck away from any magnets
:) )
Regarding the article on SF rail replacing disk drives, to avoid
"catastrophic failure".... recall a while back, ActionRetro made a RAID
out of floppy disk drives (3.5"'s). With all the firmware going into
modern
SSD's and M.2's, I ponder the irony of
"old dumb mechanical drives"
actually being (in a way) more secure.
-Steve
On Tue, Oct 29, 2024 at 8:35 PM Fred Cisin via cctalk <
cctalk(a)classiccmp.org>
wrote:
> On Tue, 29 Oct 2024, Chuck Guzis via cctalk wrote:
>> The location of track 0 is radically different in the 96 tpi and 100
tpi
>> conventions--there's about a 6 track
offset. 100 tpi drives were also
>> spec-ed as being 77 track (like their 8" relatives).
> Are the tracks offset from one side of a disk to the other?
>
>