Looks like a standard 5.25" drive to me - there was nothing special about the 5.25" drives IBM used on the XT - even my old
SA-400's from my Altair would work (IIRC the SA-400 was the first 5.25"drive) - although the SA-400 was only single sided.
IIRC there was a single-sided format optiom in DOS.

The only thing "weird" about the PC drive setup was the cable twist with caused both drive A: and B: to be jumpered as drive#2
(so non-tech people didn't have to set jumpers when adding a drive) - the original 5.25" spec has 4 drive select signals.

Later on when HD became a thing, drives differed more - but that looks pretty normal to me (If using it on a PC, be sure to
set the select jumper for drive#2) - IIRC during my more floppy active days developing ImageDisk - I had at least one Mitsubishi
drive - and I don't recall any particular problems with it.

Should be easy enough to give it a try.

Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal

Is there a way to tell if it's a SS (180K) or DS (360K) drive without hooking it up?

Tempest wrote on 2024-08-14, 18:44:

Is there a way to tell if it's a SS (180K) or DS (360K) drive without hooking it up?

Oh that's easy. It has two heads, so it can't be single sided drive. A closer inspection of the head could also tell you if that's a DD/QD or HD drive.

Deunan wrote on 2024-08-14, 18:55:

Tempest wrote on 2024-08-14, 18:44:

Is there a way to tell if it's a SS (180K) or DS (360K) drive without hooking it up?

Oh that's easy. It has two heads, so it can't be single sided drive. A closer inspection of the head could also tell you if that's a DD/QD or HD drive.

Yes, but just to be more clear what to look for, looking at your drive view from the top. you can see the "upper" head - this is
the head that is spring pressed against the media when it is inserted, on the side away from the motor.
The lower head is the one on the spindle motor side, which does not raise/lower - you photo shows the upper head
as fairly wide (holds a head) with wires going to it.

A single-sided drive does not have an upper head, instead it usually has a much smaller pad which
presses the media against the lower head, and is not wired to anything.

IIRC there were very few "standard" single-sided 1/2 height drives. I did see a few system specific
specialized 1/2 height SS drives, but I don't think I ever saw one with a standard interface - I did see a
few full-height ones.

I don't have any to show you, but I did find a photo online that shows the "upper" side of
Single-sided drive - note the pad instead of the upper head, compared to the size of the actual
head (lower).

https://commons.wikimedia.org/wiki/File:RX50_ … ssembled_03.jpg

Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal

Can you photo the sticker that tells the model's name? It's usually on the back or the side. The print on the bottom is for the spindle motor maker, and is not indicative of the drive's model (many companies took spindles from Matsushita or Mitsubishi).

Don't laugh, but I find a good indicator if the drive is 360K is if its activity LED is red. If it's green I'd swear it's a 1.2MB drive. A definitive answer is if you hook the drive to the PC and specify it as the wrong format.. typically you'll get a "diskette drive error" right away during POST.

Finally, if you're experienced you can get a photo of the head stripes and tell from their thickness (360K is thick, 1.2MB is usually less than 1mm in thickness).

There is a possibility the drive is not for IBM too. Best thing is to start from the model name on the sticker.

Based on the photos I think the drive is the MF501C like this picture, which is a 36ok drive...and manual
https://minuszerodegrees.net/manuals/Mitsubis … ion%20Guide.pdf

Thank you everyone. I'll give it a real test this weekend when I have my 486 open and see what it detects the drive as.

wbahnassi wrote on 2024-08-15, 03:32:

Don't laugh, but I find a good indicator if the drive is 360K is if its activity LED is red. If it's green I'd swear it's a 1.2MB drive. A definitive answer is if you hook the drive to the PC and specify it as the wrong format.. typically you'll get a "diskette drive error" right away during POST.

I guess you're right in that many 360k used red activity LEDs, but many 1.2meg drives also used red, including the ALPS drive used in the IBM AT.
I currently have a Fujitsu branded 1.2meg drive in my 486, and it also has a red LED.
Green was more standard with the 3.5" drives (though I also have one that uses red)

I don't think there's a simple visual-only way to tell them apart.
There are a few "hints" that seem to be more common on 1.2HD drives, but not always
- Green LED
- White Bezel
- Upper head has metal shield over it (I've seen this on 360k, but more common on 1.2)

There are electrically a couple of things which are much more certain:

If you happen to have an oscilliscope or frequency counter... 360 rotates at 300RPM and
1.2 at 360RPM - a bit of tape sticking up from the spindle and an IR LED/detector
can make it easy to read the spindle speed...

If you have ImageDisk, there's a test/analyze function where you can make the
drive step to any track ... 360k has 40 tracks, 1.2 has 80 ... move it to track 39
and see if the head it at the inside (360) or near the middle (1.2).
(Depending on the track stepper motor, you may be able to figure this out by
"feel" - but never easy or reliable)

Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal

DaveDDS wrote on 2024-08-15, 20:44:

If you happen to have an oscilloscope or frequency counter... 360 rotates at 300RPM and
1.2 at 360RPM - a bit of tape sticking up from the spindle and an IR LED/detector
can make it easy to read the spindle speed...

Even simpler if you don't mind having a diskette in it while spinning it up.
There's already is a IR LED and detector - the index sensor.. All you need to do
is scope the index sensor and you see either 300 ticks/second (360k)
or 360 ticks/second (1.2m)

Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal

The sticker on the motor says 300rpm, is that a clue ? ;p

Horun wrote on 2024-08-17, 22:34:

The sticker on the motor says 300rpm, is that a clue ? ;p

Ha, I didn't even notice that when initially looking at your photos.

If it is accurate, YES - that would indicate a 360k drive.

Unfortunately you often can't "trust" things like this. It was not-uncommon
for drive manufacturers to use two-speed motors (so they could stock the same
motor for DD and HD drives - the sicker saying "300rpm" probably indicatges
the only speed the drive could do -- but! - it may indicate that a two-speed
drive was jumpered for 300rpm when it left the factory, which might have
been re-jumpered to 360rpm by the drive manufacturer (I've seen things like
this). Given the both are Mitsubishi - it's most likely that the sticker is
accurate.

On my ImageDisk page I have some notes about modifying a certain Panasonic
drive I was a fair bit back-in-the-day to put a 300/360rpm switch on the
front bezel (Some SD formats couldn't be read by the PC FDC/data-separator
at 360rpm).

Also, your drive not having a shield over the upper head is another good sign
that it's a 360k - I saw a few 360's without such a shield, but I don't think
I saw a 1.2 without one.

Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal