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View Full Version : 48 tpi on a Tandon TM-100-4?



marmotking
February 4th, 2009, 02:23 PM
So, I bought what I thought were 40 track, double sided, double density drives...only to find out that they're TM-100-4 drives...which are 80 track (i.e. 96 tpi). Now I could use them as 80 track drives and will if necessary. But, I'd like to know if there's a way to use them as 48 tpi drives. It doesn't appear there's any sort of jumper that can switch this. I don't know if it's a function of the controller board, or the stepping motor or both. Would swapping a controller board from a mechanically bad TM-100-2 to the TM-100-4 make it a 48 tpi drive? I'd assume that the -2 and the -4 must have different stepping motors. Any information would be greatly appreciated.

patscc
February 4th, 2009, 02:37 PM
Your biggest problem will be the fact that the 80 track have a narrower head gap, since they have to write narrower tracks. This is a physical limitation. It's the 360k & 1.2 M floppy problem, and you can read more about it here:
http://www.retrotechnology.com/herbs_stuff/drive.html
patscc

MikeS
February 4th, 2009, 03:05 PM
Wait a few days; there may be folks who'd be willing to trade you 48TPIs for those 96s.

Fallo
February 4th, 2009, 04:34 PM
Your biggest problem will be the fact that the 80 track have a narrower head gap, since they have to write narrower tracks. This is a physical limitation. It's the 360k & 1.2 M floppy problem, and you can read more about it here

Yes, I've been wanting to get a 5150 or XT (and maybe a Tandy 1000), and this is one little thing that I've been concerned about. I've got 5.25" drives in my 386 and my Pentium, but both are HD (a Teac and a Panasonic combo drive). Now, I've heard from various sources that not all HD drives will screw up DD disks, but I don't know exactly which ones. The original IBM AT drives were said to be the worst.

billdeg
February 4th, 2009, 05:02 PM
So, I bought what I thought were 40 track, double sided, double density drives...only to find out that they're TM-100-4 drives...which are 80 track (i.e. 96 tpi). ... Would swapping a controller board from a mechanically bad TM-100-2 to the TM-100-4 make it a 48 tpi drive? I'd assume that the -2 and the -4 must have different stepping motors. Any information would be greatly appreciated.

Assuming you're using DOS, use sector and track switches with your DOS format command to format the disk to match the 40 track double sided. These instructions are in older DOS manuals, 3.3 for example. Once the disk is formatted to use 40 tracks, the drive will act as if it's a 100-2a

right? I am not near a DOS manual at the moment, but I am sure the switches are on the web or this web site even.

Bill

patscc
February 4th, 2009, 05:43 PM
You still have the issue with the relative width of tracks, and this is something you can't overcome with various format switches. There's a link in my previous post that gives a pretty good summary of the various permutations of DD & HD, etc. It really is worth a read.
And here's the link again:
http://www.retrotechnology.com/herbs_stuff/drive.html
patscc

Chuck(G)
February 4th, 2009, 06:09 PM
Nope, these drives look like 720K 3.5" drives (without the disk change line) to DOS. You can format and use them as 720K.

Unfortuntely, the double-stepping used on 1.2MB drives by the BIOS won't work, as the data rate is different (i.e. you can't call them 1.2MB drives).

If you want, I think I've got an MS-DOS driver that will double-step these things to fake 360K access under DOS.

Changing out the drive PCB won't matter--the 96 tpi is part of the positioner mech (stepper angle and capstan), not the electronics.

Check the part number again--if they're 4M, and not 4, you probably will have some offers to swap or purchase as the 4Ms are 100 tpi drives.

patscc
February 4th, 2009, 07:23 PM
Right, forgot that they're quad 5.25's, for some reason I thought they were 1.2 Mb drives.
However, the tracks are still narrower than on the 360k drives.

Wouldn't the old drivers.sys or dosparm trick work as well ?
patscc

Chuck(G)
February 4th, 2009, 07:40 PM
Right, forgot that they're quad 5.25's, for some reason I thought they were 1.2 Mb drives.
However, the tracks are still narrower than on the 360k drives.

Wouldn't the old drivers.sys or dosparm trick work as well ?
patscc

Not if you want 360K access. Double stepping is done by the BIOS, not the driver; the BIOS supports double-stepping only on 1.2MB drives, which spin at 360 RPM, not 300, and so use the 300Kbps data rate. With the quads, you need 250Kbps because they're 300 RPM drives. Now, if they were 4Ms, the spindle speed would be right, but the tracks fall in the wrong place.

patscc
February 4th, 2009, 07:44 PM
Right,right. I keep forgetting about quads, never having owned on. Wouldn't mind a couple, though, even dead ones, if anyone has any to spare.
patscc

Chuck(G)
February 4th, 2009, 07:52 PM
Right,right. I keep forgetting about quads, never having owned on. Wouldn't mind a couple, though, even dead ones, if anyone has any to spare.
patscc

I've got a few--all HH, though; mostly YE Data.

MikeS
February 4th, 2009, 09:37 PM
Assuming your drive has the relevant jumpers to set the speed and current, can't you just use 1.2HD drives as QD drives?

Terry Yager
February 4th, 2009, 09:56 PM
Right,right. I keep forgetting about quads, never having owned on. Wouldn't mind a couple, though, even dead ones, if anyone has any to spare.
patscc

I'll send you a pair, along with the Model 4 stuff. Pm or call me...

--T

Chuck(G)
February 4th, 2009, 09:58 PM
Assuming your drive has the relevant jumpers to set the speed and current, can't you just use 1.2HD drives as QD drives?

Absolutely.

Terry Yager
February 4th, 2009, 09:59 PM
Assuming your drive has the relevant jumpers to set the speed and current, can't you just use 1.2HD drives as QD drives?

96 tpi, yes, but 100 tpi...???

Wasn't Andrew looking for some 100 tpi drives awhile back?

--T

NobodyIsHere
February 5th, 2009, 02:29 AM
96 tpi, yes, but 100 tpi...???

Wasn't Andrew looking for some 100 tpi drives awhile back?

--T

Hi Terry! Yes, I was searching for 100tpi Tandon TM100-4M floppy drives since they are needed for the Vector Graphic machine. If these drives do prove to be the -4M models I would definitely like to discuss with the original poster.

However, they appear to be the more common 96tpi -4 models which can be usually substituted with Panasonic JU-475 style drives and Teac FD55GFRs as Mike and I discovered a few months back working on getting the VG to boot with non-100tpi floppy drives.

If you can use the 1.2MB HD floppy drives converted to DSQD mode, I would definitely do that before using the TM100-4 or TM100-4M. Those drives are rare and worth preserving especially the -4Ms as they are the only thing that can read 100tpi media.

Thanks and have a nice day!

Andrew Lynch

Chuck(G)
February 5th, 2009, 01:57 PM
HIf you can use the 1.2MB HD floppy drives converted to DSQD mode, I would definitely do that before using the TM100-4 or TM100-4M. Those drives are rare and worth preserving especially the -4Ms as they are the only thing that can read 100tpi media.

Andrew, I believe it was Micropolis that originated the 5.25" 100 TPI floppy. I've got a couple of their drives, as well as the MPI 100 tpi version. So the Tandons are by no means the only ones.