Re: AEHD drive

[supertimer@aol.com (Supertimer)]

Pim Blokland <nipp@nipp.nl> wrote:

>I have a AE HD drive connected to my GS, but it turns out this drive 
>cannot read 1.44MB disks. If a HD diskette is inserted, it wants to 
>initialize it as 1.6MB.

That's because the IIGS built in controller, the IWM, can only
use GCR encoding.  This encoding is used in Mac and Apple II
800k disks.  Both HFS and ProDOS 800k disks are GCR
encoded.  If GCR is used in high density disks, what do you
get?  Double 800k, or 1.6MB.  But when Apple increased Mac
floppy storage, they knew the PC was a bigger standard, so
they switched to MFM encoding in the 1.44MB format.  This
allows the PC to read and write Mac 1.44MB HFS disks with
the right software.  The older IWM cannot handle MFM
encoding, so the IIGS cannot make 1.44MB disks on an
AE HD drive without extra hardware (namely, a SWIM
controller provided by a SuperDrive card).  It can, however, do
1.6MB GCR encoded high density.

>Now I remember reading something about the AEHD, but I can't find 
>anything about it, apart from the fact that it exists.
>So my question is: How do you make this drive work with the world 
>standard 1.44MB format?

The IIGS can indeed do this with the AE HD drive, but you
need to attach the drive to an Apple II SuperDrive controller.
When attached to the controller, the drive does 1.44MB
high density disks.  To use 1.6MB high density disks, you
would have to plug the drive back into the IIGS' built in
controller.