See my one comment embedded below, plz.
Dick
-----Original Message-----
From: Tony Duell <ard_at_p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Sunday, April 18, 1999 2:08 PM
Subject: Re: z80 timing... 6502 timing
>>
>> I want to distance myself from the majority of this nonsense. Building a
>> simple computer with a processor, a ROM, a full compliment of RAM, and a
>> serial console interface is a 10-minute design and a 90-minute
fabrication
>
>Less than that, actually. There's nothing to 'design' IMHO - just stick
>the chips on a piece of wire-wrap board and wire-wrap the address and
>data buses. While you're doing that, design the address decoder with the
>other half of your brain.
>
>I built a 6809 SBC years ago, and the chip count was pretty minimal.
>IIRC:
>6809 CPU + 4MHz crystal as the clock
>2 off 6264 RAMs (16K RAM total)
>2764 EPROM and space for a second one
>6551 + MAX232 serial port
>9914+75160+75162 GPIB port (that was in the spec, obviously not needed
>for a general-purpose machine).
>2 off 74LS138 address decoders (one to divide the memory map up into 8K
>blocks, the other to subdivide one block for the I/O chips). These days
>I'd use a GAL.
>A couple of TTL latches and buffers for I/O ports (cofig switches, status
>LEDs, etc).
>
>That was it. Obviously a 6502 could be used with much the same hardware.
>A Z80 wouldn't be any worse either.
Rockwell made a 65C102 available in the same speed grades as the 65C02.
This used a quadrature clock just like the 6809 and worked pretty much like
it as well, at least insofar as the timing circuit was concerned.
>> Now I can't imagine why a graphics display, or anything so inane as that
>> could creep into the consciousness of an otherwise perfectly sane person
>> wishing to deal with one of life's fundamental mysteries, i.e. "which is
>> really faster, the XXXX or the YYYY?"
>
>Oh, Sam was suggesting all sorts of complex features and I was pointing
>out that most of them weren't that hard to add if you really wanted them.
>You don't want them for this challenge IMHO.
>
>-tony
>
Received on Mon Apr 19 1999 - 00:01:53 BST