34 replies to this topic

[Larry]

Bob beat me to it, but 4D is not HD. HD is HD. That's why those disks work. They used to have 80-track DD drives (5-1/4") -- and not very reliable mechs that I encountered, anyway.

-Larry

[Marius1976]

Larry, on Thu Jan 26, 2012 2:15 AM, said:

Bob beat me to it, but 4D is not HD. HD is HD. That's why those disks work. They used to have 80-track DD drives (5-1/4") -- and not very reliable mechs that I encountered, anyway.

-Larry

Ah... there you go. That's it indeed. I supposed (and I was wrong) that 4D = High Density. But it's obviously that a Double Density disk = 360K, and Quad Density will be 720K indeed. You are right.
Cool... so my 4D disks can be used!

Greetz
M.

[Marius1976]

@bob1200xl the Bas-F HD disks I have do have AND a hub ring, and that 'black' oxide. I suppose these are that High Frequency disks too?

[Larry]

BTW.

David Small wrote an article for Antic magazine on connecting a 5-1/4" (40 or 80-track) drive to an ST. Might still be interesting reading.

These 80-track drives were quickly made extinct by the much smaller, more nimble 3-1/2" drives, so I suspect they are really, really rare these days.

http://www.atarimaga...esibmdiscs.html

-Larry

[bob1200xl]

I think I have some high frequency disks with hub rings - and some low frequency disks without. The 'color' of the coating is very subjective. Only way to tell for sure on some disks is to format them.

Bob

Marius1976, on Thu Jan 26, 2012 5:52 AM, said:

@bob1200xl the Bas-F HD disks I have do have AND a hub ring, and that 'black' oxide. I suppose these are that High Frequency disks too?

[ijor]

5.25 HD disks, and 3.5 HD disks are quite different beasts. Or more precisely, the relation between DD and HD in 5.25 disks is very different than the one on 3.5 disks.

3.5 HD disks are more similar, in their magnetic properties, to DD ones. They have a much closer magnetic "coercivity" than 5.25 disks. So it is quite common to be able to use 3.5 HD disks as if they were DD disks. On the other hand, most of the time you try to use 5.25 HD disks with a DD drive, it will fail.

Another difference is that 3.5 HD drives detect the disk density automatically, by sensing a specific hole in the disk. 5.25 drives can't do the same. The controller must tell the 5.25 drive to use HD or DD mode.

[Marius1976]

@ijor

Tanks for your contribution!

One thing is strange about it. In my start post I wrote that I know (a few) Atari ST owners who do as if the DD Atari ST disk drive won't handle HD 3.5" disks very well. Probably because of the same reason a few people explained here concerning 5.25" disks.

Do you agree with that, or do you have another opinion?

[Rybags]

The bottom line is you'll often get them to work but in no way should depend on them for long-term storage.

I've also found that the HD 3.5 floppies don't work near as well for transferring stuff as they used to, probably thanks to age of the ST drives and disks themselves.

[ijor]

Marius1976, on Mon Jan 30, 2012 8:07 AM, said:

One thing is strange about it. In my start post I wrote that I know (a few) Atari ST owners who do as if the DD Atari ST disk drive won't handle HD 3.5" disks very well. Probably because of the same reason a few people explained here concerning 5.25" disks. Do you agree with that, or do you have another opinion?

Well, in matters like this, you know what they say, YMMV !

But usually, it is much more reliable to used 3.5 HD disks as DD ones, than to use 5.25 HD disks in a DD drive. Most people can use HD disks with ST drives, and most people can't use 5.25 HD disks on any 5.25 DD drive.

Note that in the ST there is a different issue of trying to use actual HD (with a 3.5 PC drive replacing the stock ST drive). That's a completely different problem, mostly related to the FDC.

[candle]

there are 2 or 4 resistors setting current available for write operations on 5.25" HD drive and selected by the onboard chip as told by the HOST,
have anyone tryed to change their values and see what the result would be?
they are quite big - usually non-flammable types (metal oxide resistors) in ceramic cover rather than plain carbon resistors