Charlie wrote:
"Steven Hirsch" <snhirsch@gmail.com> wrote in message 1p6dnXqfLPZZdhXUnZ2dnUVZ_jOdnZ2d@giganews.com">news:1p6dnXqfLPZZdhXUnZ2dnUVZ_jOdnZ2d@giganews.com...Charlie wrote:"Steven Hirsch" <snhirsch@gmail.com> wrote in message YdKdnWEBU6Dx5RXUnZ2dnUVZ_h2WnZ2d@giganews.com">news:YdKdnWEBU6Dx5RXUnZ2dnUVZ_h2WnZ2d@giganews.com...Yes, Disk2FDI manages to read Apple 3.5" disks in PC type (single speed) 3.5" drives.Alex Freed wrote:Wouldn't it be possible to cleverly emulate the variable speed zones in software by playing with the data rate? (For some value of cleverness at any rate).sicklittlemonkey wrote:Are you talking about reading actual Apple II disks, a la FDI etc, or just reading and writing to modern HD media via an emulation of 5.25 & 3.5 GCR formats?After posting I remembered that the Apple 3.5" disks were "special". AFAIK they use variable speed to using a PC drive to read/write Apple 3.5" disks is at least difficult.SteveI didn't realize that disk2fdi worked with 3.5" drives!It also supports 3" drives (whatever they are) and 8" drives. I've found when reading 3.5" Apple II disks there is an occasional disk that won't read in either the upper tracks or the lower tracks. Using a different 3.5" PC drive usually cures the problem.Another example is the Copy II Plus option board. Unless I'm confusing it with something else, it was able to read and duplicate 800K Mac diskettes (same low-level format, I think).I'm not familiar with the Copy II Plus board but another interesting card is the PC Transporter. It can read/write an Apple II 3.5" drive in either GCR with the variable speed (800K) or PC MFM with single speed (720K). In this case though, I don't believe the speed is done in software. If I remember correctly the PC Transporter somehow keeps the speed from varying in the drive.
PC drives are not even capable of the "zone" speed changes that Apple 3.5" drives do. To read or write an Apple GCR 3.5" disk with a PC drive requires changing the bit clock rate. -michael ******** Note new website URL ******** NadaNet and AppleCrate II for Apple II parallel computing! Home page: http://home.comcast.net/~mjmahon/ "The wastebasket is our most important design tool--and it's seriously underused."