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Cpyat2pc

S

Shadow Lord

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While doing a search for Quaid Disk Analyzer (prompted by this thread) I ran into this ad (left lower corner). It talks about a program that allows writing 360KB disks on a 1.2MB drive and have them remain readable on a 360KB drive. I am guessing the program purposefully adjust tracks to compensate for the narrower track width on the HD drives. Anyone have an experience with this and know how it worked?


Thanks.
 
There were a few similar shareware utilities. None of them produced disks that worked with every 360 kB drive. I think the place I worked for in 1990 purchased a copy in the hopes of doubling the number of diskettes that could be produced but it got dumped in the back room and bunches of normal 360kB drives were added instead.

If cpyat2pc is the product I am thinking of, it was slow (roughly 3 times as long to fill a disk) and applications couldn't write directly to diskette. Instead, the special program would copy files from hard disk to 360kB diskette.

Edit: The only review I can find a reference to is in the Nov 1988 issue of Foglight. Can't find the issue though.
 
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Has anyone actually archived a copy of CPYAT2PC? $79 seems like a lot to spend to solve something which even the company selling it admitted was only "sometimes" a problem, and only with older 360K drives, as this article says with newer 360K drives, the compatibility problem had largely been solved:

books.google.com

U-M Computing News

books.google.com
problemsolved.png
 
In those days that people quite often had to exchange data between XTs and ATs, we had the best results with using new unformatted 360 KB floppies, formatted by the AT, to move data from the AT to the XT and using 360 KB floppies, formatted by the XT, to move data from the XT to the AT. The theory behind using new, hopefully, unformatted floppies: when a XT has to read the smaller track of the AT, the signal will not be disturbed by the rests of a former broader XT track. We had reasonable proof that this worked.
We hardly had trouble writing with XTs to disks written by ATs before but the idea behind using "XT-only" floppies was that the smaller AT track could cause an unevenly distributed signal. No real proof if this worked but the idea was: if it doesn't work, at least it won't hurt.
 
For those teaching forensics classes, I made a device driver that hid a second 360K drive's worth of information on a DD disk written in a 1.2MB drive. Since the BIOS automatically double-stepped those drives, the students had to scratch their heads a bit to find the hidden data. :)

The Cpypc2at product did not work on all 1.2M drives, which is why it never became a thing.
 
Peter Norton actually blamed the problem on older 1.2MB drives, saying the track they wrote was not properly aligned with the head of 360K drives, so in some cases writing data to a 360K disk using a mixture of 360K and 1.2MB drives would result in a disk that was not readable in either of them. Later 1.2MB drives fixed the problem, he claimed.
 
One drive being properly aligned and another not, plus taking in account that the tracks are smaller and thus more vulnerable to mis-alignment, would mean I should have run into 1.2 MB drives not being able to read 1.2 MB floppies written by other drives. I cannot remember having run into such cases. I won't call it a BS story but I do have strong doubts.
 
There was a lot of variation among manufacturers about the type of erase used--straddle vs. tunnel. I can't verify that this has anything to do with the variability, but I suspect it as a factor.
 
Looking at the ECMA standard, the 5.25" High Density drive might only provide about 1/3 of a track width to the 40 track drive. That factors in the minimal permitted track width and maximum track deviation so only 0.11 mm of track would be available instead of the standard 0.155 mm. The 40 track drive has a 0.3 mm track. Thus, there could well be enough track for the 80 track drive to get a coherent signal but not the 40 track drive. Actual design changes to read write heads through the 80s is not information I have.

The problem with this utility is the price was about the same as a 360K drive which would provide disks that worked in other 360K drives 100% of the time unless significantly out of alignment. I had hoped to find a review which indicated how more high density drives would successfully create a 360k disk with this utility as opposed to just with DOS.
 
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