Re: Questions about IWM

["PZ" <skierpaul@yahoo.com>]

Not counting MacIntosh models, the IWM chip was used in the

>IIc - 5.25 (rom 03 added unidisk support)
>Liron Card - Unidisk 3.5
>UniDisk Drive - (internal)
>IIe PDS card (for the Mac). 5.25 and Unidisk 3.5
>IIc+ - 5.25, unidisk or Apple 3.5
>IIgs - 5.25, unidisk or Apple 3.5

Also used in Apple's IWM Disk II controller (5.25 only) and the Apple
Universal Controller (could do 800k 3.5's):

http://apple2.org/images/InterfaceCards/images/Hard.FloppyDisk/image-html/IWMDiskIICTRLr.html
http://apple2.org/images/InterfaceCards/images/Hard.FloppyDisk/image-html/UnivCTRL'r.html

The Universal Controller was essentially the IIc+ drive logic on a
card.  In addition to what was on the IWM Disk II controller, Apple
added more firmware and some additional custom logic to implement block
access to something like the 800k 3.5.

The IWM Disk II controller shows exactly how much of the original Disk
II controller is inside the IWM, pretty much all of it.  What got
consollidated:

556 - essentially a Dual 555 timer
74LS00 - only 1 AND gate is used.
74LS05 - handful of high output inverters
74LS132 - some Schmitt Triggers
74LS174 - handful of D-type Flip-Flops
74LS259 - 8 bit addressable latches
74LS323 - 8 bit universal shift/storage register

The SWIM is essentially the IWM + and an 1.44M MFM controller on one
chip.

- Paul