Magazine retrospectives

From: Brett <danjo_at_xnet.com>
Date: Sat May 17 15:41:40 1997

On Sat, 17 May 1997, Tim Shoppa wrote:
> > I've heard incredible things about the Apple ][ Disk drive. One, that it
> > took only 5 ICs for the hardware, and now only 256 bytes of code to read
> > from it? I'd really like to see both the schematics and the code. That's
> > just incredible.
>
> The 256-byte-long bootstrap for the Disk ][ is really quite long,
> as the very simple hardware needs extensive help from the software
> to read anything from the disk. The very complex hardware/software
> interaction is well-documented in Worth's and Lechner's _Beneath
> Apple DOS_, still available new from Quality Computers. The
> schematics are published in the back of both the Apple DOS 3.2
> and 3.3 manuals, though the schematics themselves don't do you
> a lot of good unless you know the programming of the bipolar
> PROM's used in the controller's state machine.
>
> For comparison, my S-100 boxes with WD1771-derived controllers have
> bootstraps that are just over a dozen bytes long.

I thought the WD-17XX and WD-19XX chips were programed to automatically
get the first track/sector on reset. I seem to remember that the other
controller chips from that time also did this. I always thought this was
the ONLY way to do it 8-) I have often thought that if all the
peripherials (did I spell that right?) did the same thing (at reset) and
made thier *internal drivers* available at boot up - it would be a much
easier world with IO. You would just have to set a switch on the IO
card/device to tell it what CPU it is working with and then be done with
it.

> For many PDP-11 disk devices, the bootstrap is only a couple words.
> When you have to toggle the bootstrap in through the front panel every
> time you boot, a short bootstrap is extremely desirable.
> Of course, in these cases, there is substantially more intelligence
> in the device and controller than there is in the Disk ][.

Oh I don't know 8-) Some of them seem pretty stupid when I try to talk
to them. They don't seem to understand that they have to work the way
I WANT them to 8-)

> Tim. (shoppa_at_triumf.ca)

BC
Received on Sat May 17 1997 - 15:41:40 BST