Apple II hardware design

From: A.R. Duell <>
Date: Sun Jun 22 22:45:38 1997

> A.R. Duell wrote:
> > I can understand why the Apple ][ has a significant following - it was a
> > machine that was 'open', that hackers could get inside, etc. But I also
> > know that it's not a good piece of hardware design, and thus don't put it
> > high up my list of interesting machines.
> I'm a newbie to the world of Apple, spending my early years with
> Timex-Sinclair's and TRS-80's. I would have to say that your statement
> above though depends on what you call a 'good piece of hardware
> design'. For me, it ranks up there with the ZX-81 as an ingenius
> hardware design due to it's simplicity. I mean heck, as far as boards

Well, the ZX81 is another machine on my 'kludge list' :-). Minimal
hardware designs do not, in general interest me....

I love board after board stuffed with TTL. I have machines with a couple
of _thousand_ chips in them, still running, and great fun to repair and

Simplicity is nice, but inginuity is even nicer. Compare the Apple ][
video system with (say) a PPL or I2S framestore for a PDP11, and you'll
see what _real_ video hardware is like (yes, I know, no comparison - the
PDP11 framestores were 100 times the cost of an Apple ][).

I've never liked bit-banged serial ports either (except on
microcontrollers). They always seem to have problems with full-duplex
operation. Yes, Apple sold a bit-banged serial port for a time - I have
one with the manual (which, amazingly contains instructions on linking it
to an ASR33), presumably to save a UART chip. They then sold one that
worked properly (in full-duplex mode, etc) under the name 'super serial
card'. It used (IIRC) a 6850 chip (or was it a 6551?)

> go, the Apple II mainboard is almost beautiful in it's layout due to
> this. I often find it interesting to think about the total 180 degree
> turn Apple did between the ][ series and the Mac's as far as
> expandability and such. They went from a totally open system to a
> totally closed system. They should've stuck with the open.

The minimalist approach to hardware was still present in (at least) the
early Macs. I was inside a Mac+ the other day, and the mainboard seemed to
consist of the expected chips (68000, ROMs, RAM SIMMs, 5380, 8530, etc)
and a few PALs + TTL stuff. How the video side works is a mystery to me...

Ditto the Apple Laserwriter 2NT (I've just been working on one). The
engine interface on the formatter board seems to consist of a few bits on
a VIA for the command/status lines, a small FIFO, a few TTL devices, a
state machine in a PAL, and (I guess) some clever 68000 software.

> As for the difference in a system using hardware to drive things or
> software, just look at the difference in some floppy drives used in
> various other things. The drives used for like the Atari 8bits were
> extremely flexible, as were those with the Amiga, while drives used on

An Apple ][ drive + controller can't (AFAIK) read a standard FM or MFM
disk, no matter how clever the software, just as a PC controller can't
read a GCR (Apple or Commodore) disk.

> any PC, regardless of age unless it has a special controller, are very
> limited to just what the hardware will let them use. Of course, I don't

This is true, but if you want to do strange things with PC (or any other)
hardware then design the card you need. It's not that hard, and it won't
affect the machine's performance in other areas.

> Jeff

The gates in my computer are AND,OR and NOT, not Bill
Received on Sun Jun 22 1997 - 22:45:38 BST

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