At 2:19 Uhr +0200 08.06.1998, Ken Nakata wrote:
>On Mon, 8 Jun 1998 00:30:23 +0200,
>Hauke Fath <hauke@Espresso.Rhein-Neckar.DE> wrote:

>> The iwm floppy driver is known to work on the SE/30, the IIsi/ci and the
>> Q700. It does NOT work on IOP machines (IIfx, Q900/950, Q840AV, Q660AV?)
>> due to different hardware.
>
>The AV's don't have an IOP, but they don't have a SWIM chip, either.

I used the term IOP somewhat loosely in the sense of "doing GCR decoding
on-chip". In fact, I have just re-read a set of snippets from technotes
Apple has online. They said about the 840AV's floppy controller...

---------------------------------------------------------------------------
>[Macintosh AV Series: Floppy Drive Performance (5/94)]
>
>This microprocessor (the new integrated floppy controller), while taking over
>all of the timing-critical floppy control functions, does not have the
>computational
>speed of the main processor, or the speed of the 68000 used in original
>Macintosh systems. The result is that for GCR formatted disks (800K), the
>additional computation used in GCR coding and decoding makes accesses to and
>from an 800K floppy slower than on previous macintosh systems. Our tests show
>that it usually takes about 50% longer to read and write to an 800K floppy on
>the AV systems as compared to other Macintosh systems. Currently, there are no
>plans to change the floppy controller for an increase in performance. The
>performance of the floppy drive in 1.44M mode is comparable to other
>Macintosh systems.
>
>The 800K read/write performance is a compromise in order to provide the
>additional functionality of those products based on the current
>technology, cost, and time to market constraints.


about the late Quadra machines

---------------------------------------------------------------------------
>[Centris 610 & 650, Quadra 800: Custom ICs (7/94)]
>
>SWIM2:IOSB contains the SWIM2 floppy disk controller.  It has
>full Macintosh SWIM2 capabilities, and is capable of supporting a
>2.88MB floppy format.


and about the PowerMacs' SWIM III

---------------------------------------------------------------------------
[Power Macintosh: Description of Integrated Circuits (3/94)]

SWIM III Floppy Disk Drive Controller
-------------------------------------
The SWIM III floppy disk drive controller is an extension of the SWIM II
circuitry used in models such as the Macintosh Quadra 800 and Macintosh
Quadra 650. It includes the following new features:

* support for DMA data transfers, which minimize use of the main processor
* no requirement that interrupts be disabled during floppy disk accesses
* support for GCR and MFM formats on 1.44MB disks
* compatibility with the manual-inject floppy disk drive

Floppy disk drives designed to be compatible with the New Age controller
used in the Macintosh Quadra 840AV and Macintosh Quadra 660AV computers
can easily be adapted for compatibility with the SWIM III controller.


-- Regarding the late Quadras: I do not quite understand why teh P630
misbehaves; in the relevant parts (SWIM initialization) the .Sony ROM code
is byte for byte identical with the Q700 ROM. Maybe it's a timing issue.

>Hey!  That reminds me of the call I made to ask the local NEC branch
>to send me a copy of the datasheet of the AV floppy controller chip...
>Maybe time to make a call again...
>
>Keep up the good work!

Will do.   =8)

	hauke


--
"It's never straight up and down"     (DEVO)