Re: IIe 3.5 disk drive controller card

[Roger Johnstone <rojaws@orcon.net.nz>]

In <qhacptbfv0.fsf@ruckus.brouhaha.com> Eric Smith  wrote:
> 
> Roger Johnstone wrote:
>> A minor correction: all Apple Macintosh drives can read and write GCR 
>> disks. Macs originally used variable rotation rate drives, but around 
>> the intoduction of the first Power Macs Apple switched to using 
>> cheaper  drives with a fixed rotation rate but which varied the data 
>> rate instead.  These drives and/or disk controllers are the ones that 
>> have problems  making ProDOS 800KB disks, at least using Disk Copy.
> 
> Well, perhaps I should have said that recent internal 3.5" drives on
> Macintoshes no longer support GCR *reliably*.  As far as I'm concerned,
> that's functionally equivalent to not supporting it at all.
> 
> Besides which, the floppy controller on newer Macintoshes can't 
> support GCR even if the drive was capable.

Where did you hear this? I think we need to clear this up:

1. All Apple floppy drives for Macintosh computers can read and write 
GCR disks.

Yes, there are reliability problems on some of the later Macs, but only 
when you then try to use the disk on an Apple II. Even then it seems to 
mainly be a problem with Apple's Disk Copy software. Obviously in later 
years Apple stopped testing compatibility with the Apple II, but these 
are still valid GCR disks since they'll work fine on another Mac, even 
an old 1986 Mac Plus.

2. All Macs with floppy drive controllers can read and write GCR disks.

The last Mac model to have a floppy drive was the original 'Beige' Power 
Mac G3 from 1997. They could handle GCR disks. The original 1998 iMac 
had no floppy drive, but still had the controller and even a place on 
the motherboard to solder a connector. I connected an Apple 3.5 Drive 
from my IIgs to my old iMac using this and it worked fine.

Of course all the Macs since then have lacked both a floppy drive 
controller and a floppy drive, and the only way to add one is to use a 
third-party external USB drive. Unfortunately because of the Mac's small 
market share and the fact that the last Mac to have GCR-only drives was 
sold in 1990, no one has ever made a USB drive which supported GCR disks.

-- 
Roger Johnstone, Invercargill, New Zealand
http://vintageware.orcon.net.nz/
________________________________________________________________________
  No Silicon Heaven? Preposterous! Where would all the calculators go?

              Kryten, from the Red Dwarf episode "The Last Day"