vanaards@p4.cs.man.ac.uk (Steven van Aardt) (03/19/91)
I believe 1.2 MB disks have a different surface coating than the smaller capacity 360/720 KB disks. And therefore the head on the drive must be different to cope with this. Obviously the head of a 40track drive is wider than that on an 80track drive, on switchable drives the narrower head is made double step when reading 40 track disks. There's no way you'll be able to read a mac disk - unless you've got a Mac drive - I believe this is because they use variable speed drives. -- --------------------------------------------------------------------------- - JANET E-mail : vanaards@uk.ac.man.cs.p4 (Steven van Aardt) -- -- Warning this user has been designated for termination on the 21.6.91 -- ---------------------------------------------------------------------------
charlesw@p4.cs.man.ac.uk (William Charles.) (03/19/91)
High density 1.2Mb disks ARE completely different from normal disks - It's a similar situation to audio tapes - You shouldn't use a metal tape on a deck that isn't designed for them - It can damage the heads... As for Mac disks, it's true that the disk is spun at variable speeds as the head moves from centre to edge... Will.
adamd@rhi.hi.is (Adam David) (03/24/91)
In <vanaards.669388334@p4.cs.man.ac.uk> vanaards@p4.cs.man.ac.uk (Steven van Aardt) writes: > There's no way you'll be able to read a mac disk - unless you've got a >Mac drive - I believe this is because they use variable speed drives. You would also need a special controller / interface to drive it. It can and has been done on Atari ST with the standard drives. There is no strong incentive for anyone to produce the hardware for Archimedes (now if there had been a 68000 I/O processor that would be a different story). There was a rumour that Macintosh disks have been successfully accessed on the ST by direct control of some of the low-level 1772 functions, if true then it should not be ruled out for the Arc. It was said to require really tight and critical interrupt control with some help from the DMA and timer chips. There shouldn't be any problem encoding and decoding group codes in software. Mac disks are perhaps rotated at different speeds but what happens in this hardware product and software (rumour?) is that the sectors are read/written at the same rotational speed but at five slightly different data transfer rates for the different areas of the disk. No flame war please! Adam David. (adamd@rhi.hi.is)