Re: Apple II 3.5" Controller and SuperDrive problems...

[dempson@actrix.gen.nz (David Empson)]

Supertimer <supertimer@aol.com> wrote:

> mkelsey@spam.eecs.wsu.edu wrote:
> 
> >From what I understood, one could neither connect a IIGS drive to the
> >UniDisk //e controller nor the //c, simply because the //e and //c
> >processor alone would never be able to keep up with the data stream.
> >This all made good sense, until I bought the Apple II 3.5" controller.
> 
> Correct.  When the IIc Plus came along, it was fast enough to use
> the GS & Macintosh style 3.5" drives.  Ironically, I am not so sure
> the IIc Plus could use a UniDisk 3.5 because of this.

As far as I know, it works fine.  The IIc+ has special hardware support
for an Apple 3.5 Drive (including its built-in one), which basically
deals with streaming the data at higher speed than can be achieved with
a CPU loop (the Apple 3.5 Drive requires a byte to be written or read
every 16 microseconds, while the UniDisk 3.5 and any Apple II 5.25"
drive requires twice that).

The accelerated CPU in the IIc+ may have meant the special hardware was
not required after all, but it is there anyway.

The special hardware is simply not used for accessing other drive types.

> 
> >I tested out a Mac 800K drive, which worked fine with the CPS UDC,
> >and it wasn't detected.
> 
> If it is one of those old pre-GS Mac 800K drives without the eject
> button, the CPS UDC is the only Apple II controller that can use
> these drives.

The main reason for this is minor differences in the control signals,
which are dealt with by the interface board in the Apple 3.5 Drive.

> >I connected a bare Macintosh SuperDrive and it wasn't detected.  I
> >then mounted the Macintosh SuperDrive in one of the IIGS drive
> >cases and the drive was detected. I popped in a 720K MS-DOS and
> >verified blocks with Copy II Plus.  No errors.  I popped in a 1.44MB
> >MS-DOS and verified the disk with no problems.  I tested out an
> >emergency Apple II 800k disk and it verified with no errors. 
> >
> >Then came the acid test.  I tried formmatting a 1.44MB disk and it
> >gets about (what sounds like) 10 tracks into formmatting and returns
> >an error.  Kindly the drive ejects the disk.
> 
> Did you format from Finder?  Use Finder or another GS specific utility
> because you want to use the GS/OS Apple 3.5" driver.  This driver
> is aware of the SuperDrive while hard coded ProDOS 8-bit utilities
> may not be.  ProTerm, for example, simply refuses to format a high
> density disk in such a drive.

This is certainly possible, but if the disk has the high density
detection hole (as it should), then the firwmare should automatically
use the correct format.  Some programs make assumptions about the disk
capacity, and have problems dealing with unexpected sizes.

There is an extra call in the SuperDrive card's firmware which specifies
the formatting method.  If this is not used, the card determines the
format automatically according to the disk type.

> >Suddenly things became VERY clear.  Apparently the mainboard beneath
> >the drive (mounted inside the IIGS drive case) is handling tasks like
> >motor speed, and the likes, during a format command, thereby limiting
> >the drives capabilities.

Not exactly.  The motor speed is fixed when the drive is being used with
an MFM disk (720K or 1440K), and the variable speed is handled
automatically by the drive mechanism for GCR disks (400K and 800K).

I would have expected this combination to work fine, as others have done
this.

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand