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Re: ProDos Disk Images
Very interesting! Is there anyone out there that's running the Apple IIe
emulation card on a Macintosh Quadra 605 or LC 475, Performa 475, or
Performa 476? All of these models (could be more but I can't remember them)
have the LC PDS slot that can host the emulation card, but it also has the
manual eject drive that's of discussion here. I wonder now if the issue
about the disk controller chip would cause problems with these machines and
the IIe card? Upgrading an LC using one of these logic board may not be a
good upgrade afterall.
--- Bryan
"Roger Johnstone" <rojaws@es.co.nz> wrote in message
3E2CE04D.2030401@es.co.nz">news:3E2CE04D.2030401@es.co.nz...
> Eric Smith wrote:
>
> > mjmahon@aol.com (Michael J. Mahon) writes:
> >
> >> I expect that the Power Mac controller does not provide the
> >> variable speed control voltage that the Superdrive floppy needs.
> >> When you format a ProDOS (800K) disk, do you hear the drive
> >> changing speeds?
> >
> >
> > The Superdrive/FDHD does its own speed control. The controller in
> > recent Macs isn't capable of GCR.
>
> That's not right. All the Macs ever made with floppy drives can do GCR
> disks. You may be thinking of the recent Macs which don't have any
> floppy controller and rely on external USB drives. All the USB floppy
> drives available are only capable of MFM disks i.e. 720KB and 1.4MB.
>
> The issue is that Macs that have manual inject drives can make 800KB
> disks which work fine on another Mac, even an old ones with the auto
> inject drives, but the disks won't work in an Apple II.
>
> I think Michael is correct and that it is the drive controller Apple
> used. The original drives they used were variable speed so that they
> could get more data on the longer outside tracks by slowing down the
> disk's rotation. From what I understand, the manual inject drives are
> fixed speed drives like those used in most other computers. To vary the
> data rate they just changed the rate at which it was sent to the drive
> instead of changing the disk speed. This would have required a new
> controller chip, so the new chip coincided with the arrival of the new
> drive.
>
> The following is some more info I posted here a couple of years ago:
>
> --------
> There seem to be two problems here, one with Disk Copy and the other
> with the drives used in later Macs. Apple has a tech note at
> http://til.info.apple.com/techinfo.nsf/artnum/n30959 which mentions
> problems with the manual inject drives used in later Macs, when
> formatting Apple II disks.
>
> There is also a problem with Disk Copy, at least on my iMac running Mac
> OS 8.1. The iMacs don't have a floppy drive, but they do have all the
> hardware required to add one. I installed a D19 socket on the side of my
> iMac so I can plug in my IIgs 800KB drive, it works perfectly for Apple
> II or Mac 800KB disks.
>
> I did some experimenting today and found disks formatted from the Mac
> Finder and with the files copied onto it boot on the IIgs, but the same
> disk created with Disk Copy failed to boot past the *** UNABLE TO LOAD
> PRODOS *** stage, neither could the disk be cataloged (I/O error).
> Checking the disk with a verify program on the IIgs, it seems that
> every block gets an I/O error _except_ the boot block!
>
> (n.b.: remember that if you get the 'unable to load ProDOS' message it
> means that the disk did start to boot, since this message is an error
> reported by the program stored in the boot block itself, but the boot
> code could not find the ProDOS file on the disk, which will be the case
> if the rest of the disk can't be read)
>
> I put the drive back on the iMac and found that the Mac Finder could
> read the disk fine. I could even get Bernie to boot from it. The disk
> was also checked on a PowerBook 5300 and worked fine. The same disk
> created with Disk Copy on the PowerBook booted and ran on the IIgs.
>
> The problem with Disk Copy on my iMac is not the disk drive (real Apple
> II drive!) or the OS version (8.1, same as the PowerBook ) or the
> version of Disk Copy (latest 6.3.3 or older 4.2 produce same results).
> The only other thing I can think of is an incompatibilty between the
> iMac hardware and Disk Copy which causes the disks to be written in some
> funny format which a Mac can still read but an Apple II can't.
>
> --
> Roger Johnstone, Invercargill, New Zealand
>
> Apple II - FutureCop:LAPD - iMac Game Wizard
> http://homepages.ihug.co.nz/~rojaws/
> ________________________________________________________________________
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