Maintaining and hooking up a Mitsubishi M4853 Floppy Drive to a modern PC

[BogdanV]

A long time ago i used M4853 drives on My BBC Micro and swapped between my PC and the Micro ( obviously switching jumpers ) Is there another number ie: M4853 - ??? or any other details on the plate ?, I should have my notes on the drives i used and will see if i can find them.

If you're referring to the Model field then no, there's nothing following the dash. Its literally "M4853 -". Serial number is G3J 54472. There's also a sticker on the back with "M4853D" on it. Could this be it?

 

[Malc]

Found some notes and this may or may not be of any use:

The closest to your " G3J " drive i have in my notes is " G3H " and " G3K "

What are the details of the Top PCB on your drive ?, Both the G3H and G3K drives i had used the same Top PCB: " Namff DC447987 00A " and the jumper setting are as follows which i know worked in my PC.

MS = Open
MM = Closed

DS
0 = Open
1 = Closed
2 = Open
3 = Open

MX = Open
HS = Open
HM = Open
HC = Closed

H R
(1) = Open
(2) = Pins 1 + 2 = Closed
(3) = Open
(4) = Pins 2 + 3 = Closed

Lastly Just above the DS Jumpers there is a row of jumpers which are the "Terminating Resistor" jumpers, You will need to close these if it's the only drive or Last drive, and you will need 7 jumper caps.

 

[Chuck(G)]

Got you both beat--I have a G3T drive here. Same PCB, right down to the 00A.

I have jumpers on the terminator positions, DS1, HC and MM.

Manufacturing date is "O 1984" Appears to be Rev. U.

 

[Malc]

Haha G3T Noted

A long time ago i modified the M4853 1.2 Mb drives so that they were switchable between 40 / 80 Track for the BBC Micro a real pain in the bum they were to do.

 

[Chuck(G)]

I wonder if using head-load on motor (HM jumper) might be better for a PC-type system.

 

[Malc]

I can't remember if i tried using the HM jumper, I don't have those drives anymore, They went with the BBC Micro's i sold a long time ago, Worth a try though.

 

[geoffm3]

I wonder if using head-load on motor (HM jumper) might be better for a PC-type system.

Can you elaborate on what that does exactly?

 

[Chuck(G)]

My manual for the 4853 (it's for the original rev, not later ones) specifies that the HM loads heads when the motor is turned on. It also mentions an HS jumper that loads heads on drive select, but my G3T drive doesn't have that jumper, but has HC, which isn't mentioned. Does anyone have a Tandy 2000 tech ref manual handy? There's a manual for the 4853 there, but I suspect that it's the same one that I'm looking at.

 

[geoffm3]

My manual for the 4853 (it's for the original rev, not later ones) specifies that the HM loads heads when the motor is turned on. It also mentions an HS jumper that loads heads on drive select, but my G3T drive doesn't have that jumper, but has HC, which isn't mentioned. Does anyone have a Tandy 2000 tech ref manual handy? There's a manual for the 4853 there, but I suspect that it's the same one that I'm looking at.

Is that basically the (for lack of better words) solenoid operated tensioning clamp found on some older single/double density 5.25" drives?

 

[Malc]

I can't find the manual i had on the M4853 but found one on the M4851 and when the jumper is installed on HC it causes a " Constant Head Load Condition " which occurs after the drive is ready and depends on how the H R jumpers are set.
Not much use as the M4851 does not have all the HR jumpers the M4853 has.

...but has HC, which isn't mentioned...

 

[MikeS]

Let me try to rephrase this.

1. What I seek to accomplish:

A. Successfully hook-up a Mitsubishi M4853 Floppy Drive to a PC with a AMD K6-2 CPU.
B. Write a bootable 5.25" diskette with MS-DOS 3.3
C. Plug the floppy drive back to my Tulip System I 8086 PC-compatible and boot off that diskette

Got it (finally ;-) )

2. What I have accomplished so far:

A:
Set up Mitsubishi M4853 Jumpers on the following pins: DS1, HS, H1R2.
Connected Mitsubishi M4853 Floppy Drive to a PC (that's the one with a K6-2).

So far, so good.

Set up Mitsubishi M4853 Floppy Drive as "Drive A: 360K, 5.25inch" in BIOS settings.

It is in fact a 720K 5.25" drive, which of course does not exist in the PC/MS world, so you'd have to spoof it by saying it's 3.5"
Apparently the BIOS and DOS recognize the discrepancy but W98 is unaware and probably just uses the first 40 tracks as though it were 360k

POST shows "Floppy drive(s) Fail (40)".

Curious.

MS-DOS 6.2 (part of Windows 98SE) shows "Error reading drive A: Abort, Retry, Fail" when trying to access A:

FWIW, the W98 DOS is 7.1 (7.0?), not 6.2, and there are major differences, and even more differences between 7.x/6.x and 3.3 when it comes to the location of the system files.

Windows Explorer from Windows 98SE can read, write and format to the 5.25inch drive.

Presumably as a 360K drive, which will presumably not work in the Tulip.

B: Got a hold of a MS-DOS 3.3 5.25inch floppy disk image file from BetaArchive
Tried writing the image to a 5.25inch floppy using RawWrite: program refused to work with the drive
Tried writing the image to a 5.25inch floppy using WinImage v3: writing to diskette triggered an Illegal Operation Error, thus crashing the program.

Not surprising; once again, that drive is not directly compatible with a PC unless the PC can be fooled into thinking it's a 48 TPI 40track 360K or a 720K 3.5" drive.

FORMAT.COM can format and write to floppy boot code compatible with its own MS-DOS version (ie. FORMAT.COM from MS-DOS 6.2 can write MS-DOS 6.2-compatible boot code BUT NOT MS-DOS 3.3-compatible boot code)
Windows98's FORMAT.COM can not write MS-DOS 3.3 compatible boot code, thus one needs an older version of FORMAT.COM - the one I just extracted from the MS-DOS 3.3 disk image.
DOS3.3 FORMAT.COM cannot run due to DOS version mismatch. Temporarily spoofing Win98's DOS version from 6.2 to 3.3 (using the dosver freeware utility) solved the problem.
For Point2:
Formated a 5.25inch diskette with MS-DOS 3.3-compatible boot code, then copy-pasted all MS-DOS 3.3 system files over.

That's not quite correct; you may be missing the fact that whichever version of FORMAT you use, the 3 system files will be taken from the system's atartup drive. Also, you should probably explicitly specify the tracks and sectors, and perhaps FORMAT with the /B option and use SYS to transfer whichever system files you want.

And this is where I am right now. Before proceeding to C., I wanted to try and make my PC boot from the 5.25inch drive as a test to make sure everything works properly.

Even if you get it working on the PC it may not work on the Tulip unless it is formatted and written as a 720K drive.

I sincerely hope this is clear enough. If not, then either my English is fubar or my brain is, for I honestly fail to see what was unclear in what I previously wrote. I'm not saying this as an insult, just that I really fail to see what was wrong in my wording.

Maybe I was the only one who didn't quite grasp what you were trying to do; where for instance did you actually mention that the point of this was to make a DOS3.3 boot disk for your Tulip? In any case, it's clear now.

So, what is the difference then? As you know, a DOS session running inside Win9x is different from one running natively on bare metal. DOS sessions are created and managed by the Virtual Machine Manager, with 16-bit DOS calls being thunked by the system. What I believe is that somehow Win98 is smart enough to compensate whatever wrong settings there are and help DOS properly access the floppy drive because DOS depends on VMM to handle its calls.

Quite possibly, but has W98 chosen the settings that you want?

 

[Chuck(G)]

Makes you wonder exactly how many versions of this drive there are.

For head load, we have:

HC - Keep the heads loaded all of the time
HS - Load the heads when drive is selected
HM - Load the heads when the motor is on

Apparently, pin 4, according to my manual is an "in use" output. My manual for the -53 and the -52 do not mention the H R jumpers either.

 

[BogdanV]

Sorry for the late reply, its been one hell of a year for me and only now did I finally had some time to get back to this.

Found some notes and this may or may not be of any use:

The closest to your " G3J " drive i have in my notes is " G3H " and " G3K "

What are the details of the Top PCB on your drive ?, Both the G3H and G3K drives i had used the same Top PCB: " Namff DC447987 00A " and the jumper setting are as follows which i know worked in my PC.

MS = Open
MM = Closed

DS
0 = Open
1 = Closed
2 = Open
3 = Open

MX = Open
HS = Open
HM = Open
HC = Closed

H R
(1) = Open
(2) = Pins 1 + 2 = Closed
(3) = Open
(4) = Pins 2 + 3 = Closed

Lastly Just above the DS Jumpers there is a row of jumpers which are the "Terminating Resistor" jumpers, You will need to close these if it's the only drive or Last drive, and you will need 7 jumper caps.

I tried Malc's notes and unfortunately the POST error message (floppy disk fail error (40)) still pops-up. I'm pretty much out of
ideas right now.