Maes
I like big butts!
Posts: 8662
Registered: 07-06 |
About floppies:
In general, DD double density drives (720 KB on the PC) should not be considered forward-compatible with HD high density ones (1440 KB on the PC). The media on higher density floppies needs stronger magnetization and cannot be written/erased reliably by lower-density drives, which expect a weaker magnetization.
Even if you take a pristine HD disk that has never been formatted and you manage to force-format it down to the lower capacity (it's possible, with some tricks that involve covering holes), and even if you apparently manage to write data to it, it may not be reliable in the future or on other drives. A used HD disk may not even be low-level formattable in some older DD drives.
Now THAT being said.... in practice, at some point in the past (early 90s?) they simply stopped using different media for DD and HD floppies to cut down on costs since DD were a dying breed, to the point that you could OVERFORMAT many so-called "DD" floppies to HD, and gaining double capacity "for free", so this discussion is pretty much moot.
For all effects and purposes, you can simply use HD floppies as DD just by covering the "high density" hole (the one without a movable write-protect tab). You need to do this because some DD drives DID check for the hole and refused to work with "HD" media.
As for Amiga floppies being unreadable in the PC...that's sadly true: the Amiga had a much more flexible floppy disk driver controller that used a lot of tricks such as variable sector length, zero track/sector-gaps, etc. which resulted in slightly larger capacities (e.g. 880 KB on a DD floppy, 1760 on a HD one). It was even able to read the infamous 400K and 800K Macintosh variable spindle-speed floppies, even when Apple stopped supporting the format (damn...that must have stung Apple users pretty badly, back in the day).
Now, Amiga games pretty used their own custom floppy formats and tricks resulting in weird capacities such as 910 KB etc. as part of their copy protection, so strictly speaking there's no well-defined "Amiga floppy format". You simply have an almost infinitely flexible controller that write to a floppy in a myriad different ways (and oh boy, they DID just that, back in the day).
You may only read/write them on the PC if you get a super-specialized piece of hardware like the CatWeasel controller.
|
11-24-11 00:01 
