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1.44MB Floppy Drive on 250K Controller

G

Great Hierophant

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I have read from multiple sources, such as Mueller, that a standard 1.44MB floppy will work just fine as a 720K floppy drive if the host computer only has a 250K floppy controller and BIOS support for the 720K floppy drive. Can anyone confirm this? Also, are you required to use DD media or would HD media work formatted to 720K?
 
I think GH means a 250Kbps controller, such as the original 5150 controller.

Yes, it's true. But be aware that 1.44MB drives are not "blind" to the media type hole and most will change their operating parameters if they see it. So if you use HD media, cover over the media type aperture. The magnetic characteristics of DS2D and DSHD media are close enough that the drive shouldn't complain.
 
Drat

Drat

Darn. I got all excited for a moment, thinking there was such a thing.
I've put 1.44's into a NEC Powermates & a Toshiba T1000 (at least I seem to remember it being a T1000) for testing purposes, and it seems to work just fine. I haven't actually checked to see how portable the resulting disks are, though.
patscc
 
Hi
Most newer 3.5s don't suport DD any more. There are a lot
of junk PC with drives that do.
As was mentioned, if you use HD disk, you'll need to cover
the hole. I've had no problems using them but others
say I should. I've even moved them to 720K drives without
problems. I did find that some I needed to completely erase
or I had a few errors.
In the 1.44M mode, the data is written deeper into the
media and may need deeper erasing.
Dwight
 
I've formatted HD disks down to 720K many times and never bothered with covering the hole, but YMMV. I've heard enough anecdotal evidence to believe that just because I've not had a problem, the possibility does not exist with certain combinations of drive/controller/media, etc. As Dwight pointed out tho, if reformatting downwards, you should format @ 720 in a HD drive, just to be safe.

--T
 
For HD drives, it's hard to go wrong with Teac FD235HF units.

However, these do not supply the READY signal (unless you have one of the early versions of the drive) that the DD FD235F and similar ilk do. You can always strap READY to ground, to force an "always ready" condition, but that doesn't always work with all systems.

I keep a bulk eraser (videotape style) on hand to degauss diskettes if I"m going to re-use them.
 
Terry Yager said:
I've formatted HD disks down to 720K many times and never bothered with covering the hole, but YMMV. I've heard enough anecdotal evidence to believe that just because I've not had a problem, the possibility does not exist with certain combinations of drive/controller/media, etc. As Dwight pointed out tho, if reformatting downwards, you should format @ 720 in a HD drive, just to be safe.

--T
Click to expand...

Hi
Some drives have pin 2 connected to force the 720k mode.
Others don't but covering the window always works.
Dwight
 
Chuck(G) said:
For HD drives, it's hard to go wrong with Teac FD235HF units.

However, these do not supply the READY signal (unless you have one of the early versions of the drive) that the DD FD235F and similar ilk do. You can always strap READY to ground, to force an "always ready" condition, but that doesn't always work with all systems.
Click to expand...
I was surprised to find out that Tandy's 720K TEAC drives support the ready line -- and DeskMate is designed to use it. When installing a DeskMate application from disk, it prompts you "Insert program disk in any drive" -- and the instant you pop the disk into the drive, it recognizes it and begins loading the files. Notice it says "in any drive" -- it monitors the ready signal of all floppy drives, and whichever one has a disk inserted is recognized and used.

Of course, these drives are non-standard by having the DC power lines carried through the ribbon cable, rather than through a separate power connector. The result of installing a standard floppy drive into one of these Tandys will not be pretty!
 
patscc said:
Does it really use it, or does it just poll trying to read a sector until it succeeds (because the disk is inserted) ?
patscc
Click to expand...
The drive access light is not on, as it would be if it were trying to read the disk.

Tandy's default floppy drive head step rate is set to 3 ms, too, which makes the drive extremely quiet in operation. Most generic PC floppy drives and controllers default to a step rate of 6 or 9 ms, which makes them more noisy and buzzy when seeking.
 
vwestlife said:
Most generic PC floppy drives and controllers default to a step rate of 6 or 9 ms, which makes them more noisy and buzzy when seeking.
Click to expand...

I've noticed this with all my floppies. Whenever you use a DD disk, the drives (both 3.5" and 5.25") make a lot of noise, but with HD disks, they are much quieter.
 
Fallo said:
I've noticed this with all my floppies. Whenever you use a DD disk, the drives (both 3.5" and 5.25") make a lot of noise, but with HD disks, they are much quieter.
Click to expand...

That's mostly because the step rate (in the SPECIFY bytes) is tied to the data rate clock. Because of the slower DD clock, it's harder to get an exact multiplier for the step rate.

So to tread further off-topic, how many floppy drives out there have buffered seek that operate on the 34-pin legacy floppy interface? Is my Micropolis 1115 the only one like this? It's a bizarre drive--the spindle motor, positioner and heads all pivot when you open the door. And while the spindle is belt-driven, it uses a toothed interrupter on the spindle as a tach, so there's no speed adjustment pot anywhere.
 
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