Re: Disk II Interface board for PC being built

[shoppa@alph02.triumf.ca (Tim Shoppa)]

In article <5uajdf$6o8$1@helena.mt.net>,
Forrest W. Christian <forrestc@lewis.mt.net> wrote:
>I posted a similar message to this one over in the emulators newsgroup.
>
>I'm working on a interface card to connect vintage disk II's to my PC.  To
>make a long story short, I can either cannabilize a prom from an existing
>disk II controller card (easy) or go through the effort of reproducing the
>prom (harder).  However, I feel that there may be some of you apple II
>users out there who would like to be able to hook up your apple 5.25
>drives to your PC's to be able to read 5.25 apple disks directly.
>Producing more than 1 or 2 of these cards would require me to reproduce
>the prom.

Reproducing the PROM isn't a big deal if you have access to a
bipolar PROM programmer.  I'd guess that you don't have access...

>So, the question is this:  Would you be interested in an ISA (PC based)
>card which would allow you to use your vintage 5.25 apple drives?  I'd
>probably sell this as a kit with assembly available if requested.  I'd
>also probably charge just enough to cover the cost of preparing and
>distributing the kits.

I've already built an ISA card that interfaces to standard (non-Apple II)
5.25" drives and lets me read and write Apple 13-sector and 16-sector
floppies.  It's really very simple; *no* decoding is done on the card.
All the card does is record the timing of flux transitions on read,
and writes appropriately timed transitions on write.  The PC-clone
does all the encoding/decoding.  (This is very similar to the
description I've heard of the Central Point Option Board).

I'm a bit surprised that you're going to the effort of reproducing
the bipolar PROM state machine.  Yeah, it's a cute design, but it's
very much tied to the timing of the original Apple ][ CPU and bus.

>On a side note, It may be just as easy for me to emulate the controller
>board in a embedded processor, which would permit me to build a serial
>port version.  If this is more interesting to you (For non-pc computers),
>drop me a line also.

For this sort of application, I would think it would be easier to just
buy an Apple II and slap in a Super Serial card.

>Either way, could you also let me know what type of dollar figure you'd be
>inclined to pay for this board.  Just wanting to know what type of budget
>I should work in.

My board has about US$25 worth of logic on it.  If I began selling them,
I'd want to do something other than wire-wrap construction :-).  I'd
estimate that for a small run (a couple dozen boards) that getting
double-sided PC boards produced would probably be $50 to $100 each.
I'd suspect at these prices most folks would just go the "buy an old II,
slap in a serial card" approach.

Tim. (shoppa@triumf.ca)