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Tandon TM101-4 drive?

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twistedpneumatic

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Hi guys,

Got a free Tandom TM101-4 drive. Looks like it needs a little work but otherwise in decent shape. Anyway, wanted to know if I could use it in a PC(either a XT class or later maybe?). I've heard that TM100-4's work but whats the difference between a 100-4 and a 101-4?
 
Both are 96 tpi DD drives (720KB), so not terribly useful on a PC, but perhaps on some CP/M system.

The 101-4 is more user-configurable than the 100-4, but otherwise, from a user standpoint, pretty much the same.

OEM manual
 
There is a manual for it on bitsavers: http://www.bitsavers.org/pdf/tandon/TM101-4_userMan_1983.pdf

That is a "quad density" drive. That is, a 96TPI drive that only does low density.

It looks like the "101" has some extra smarts on the logic board, but otherwise I would expect that to interface with an IBM PC floppy controller.

The catch is IBM PCs and DOS never officially supported "quad density" drives. When attached to a PC it looks more or less like a 3.5" 720k drive. You can format most 360k double sided double density 5.25" disks with 80 tracks instead of 40 for a capacity of 720k (or slightly more if you cram in extra sectors).

Since it is 96 TPI, it would have to double-step to read a standard 360k disk, and depending on your system it may not know to do that, since 3.5" 720k drives don't normally do that.

Also, since it is 96TPI, you will probably run in to the same reliability problems writing 360k disks as 1.2mb drives have.
 
SomeGuy said:
There is a manual for it on bitsavers: http://www.bitsavers.org/pdf/tandon/TM101-4_userMan_1983.pdf

That is a "quad density" drive. That is, a 96TPI drive that only does low density.

It looks like the "101" has some extra smarts on the logic board, but otherwise I would expect that to interface with an IBM PC floppy controller.

The catch is IBM PCs and DOS never officially supported "quad density" drives. When attached to a PC it looks more or less like a 3.5" 720k drive. You can format most 360k double sided double density 5.25" disks with 80 tracks instead of 40 for a capacity of 720k (or slightly more if you cram in extra sectors).

Since it is 96 TPI, it would have to double-step to read a standard 360k disk, and depending on your system it may not know to do that, since 3.5" 720k drives don't normally do that.

Also, since it is 96TPI, you will probably run in to the same reliability problems writing 360k disks as 1.2mb drives have.
Click to expand...

Say I used a later pc like one from the 90s. Would that be able to double step it for 360k? Is there a driver for DOS that I could use?
 
If you don't care about double-stepping, declare it as a 3.5" 720K drive. It'll work just fine.

Driver? Don't know--there wouldn't have been much call for this.
 
Chuck(G) said:
If you don't care about double-stepping, declare it as a 3.5" 720K drive. It'll work just fine.

Driver? Don't know--there wouldn't have been much call for this.
Click to expand...

My goal is to use it as an intermediate drive to get data to my XT machines. Is it possible to read/write normal 360K disks then?
 
That is likely the wrong drive to get data to the XT. It has the same skinny track problem that the 1.2 MB drives do. Disks written on that drive may not be readable on the XT's drive.

I believe there were drivers* to get quad-density drives to skip tracks and read the standard 40 track formats. Necessary with some of the non-IBM PC systems that shipped with quad-density drives. I did a quick check of shareware collections from before 1990 and didn't turn up any such program though.

https://stardot.org.uk/forums/viewtopic.php?t=7680 is an exploration of how to get such a drive working with a modern PC. There are probably other similar threads involving Sharp users placing quad-density drives on PCs but I didn't turn up a good link.

* Probably won't be loaded as an MS-DOS driver given when any such utility would have been written.
 
I believe that some of the Sanyo MBC-500 series had a 96 tpi option, but that thing is so far removed from standard PC hardware that it's not likely that anything there would work.

Now, having said all of that, bit 5 in location 40:90h and 40:91h controls double-stepping. I've never tried it, but you could declare the thing as a 360K or 720K drive, insert media and read track 0, then set bit 5 and see if that does anything. Or you declare the drive as 1.2MB and reset the data rate to 250Kbps directly.

I suppose you could also hack the drive to spin the disk at 360K RPM and tell the BIOS that it's really a high-density drive.

You can write a separate driver--it should be pretty simple, but it won't be Win9x or WinNT+ compatible (real mode only). But why? If you need 96 tpi capability, 1.2MB drives are not uncommon and you get the benefit of high-density as well as 720K operation.

If you don't need DOS file access, you can tell ImageDisk to double-step. This might be useful for creating physical floppies from images.
 
A bit of a side note about use of the Tandon TM101-4. In the late 70's - early 80's, my desktop machine was an early model Heathkit H89. I subscribed to Remark, Sextant, and Bus: publications aimed toward the users of the various Heath/Zenith computers. In one of those, there was an article describing using the Tandon TM101-4 and some patched code to allow storage of 400k on a hard sectored 5.25 inch disk instead of the usual 100k provided using the stock hardware and software. I don't remember if you could upgrade the boot drive in the H89 itself, but i did perform the steps necessary to upgrade both drives in an H17 dual drive unit connected to my H89. If i recall, and I may have missed a few memory refresh cycles in the intervening 40+ years, the difference between the TM100 and the TM101 was something to do with PLL circuitry in the latter giving better motor speed control.
 
When I purchased my 5150, the floppy kit came with the controller card and a single floppy. A second floppy was extra and more expensive. I had a Micropolis 1115-6 96 tpi drive (still have it) that I dropped into the second floppy slot. Initially, I used only the first 40 tracks until DOS 2.0 came out--after that, I wrote a driver to enable the use of the entire disk. Before I bodged up a Shugart SA1000 8" hard disk, it was the best I could do for storing more than 360K of data at a time.
 
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