z80 timing... 6502 timing - test-drb@ccmp.vtda.org

18 Apr 1999

please see the embedded comments below.

Dick
-----Original Message-----
From: Tony Duell &lt;ard(a)p850ug1.demon.co.uk&gt;
To: Discussion re-collecting of classic computers
&lt;classiccmp(a)u.washington.edu&gt;
Date: Sunday, April 18, 1999 2:05 PM
Subject: Re: z80 timing... 6502 timing

...
 >
> If one were going to put an FDC in place, the easiest probably would be the
...
   WD3765, since
it has built in cable-drivers and receivers as well as 
Sure. Or one of the similar, but incompatibly pinned-out UMC disk
controller chips.

Heck, it wouldn't be hard to add one of the multi-I/O chips from a PC I/O
card and have FDC, 2 serial ports and a printer port. Most of them only
need an 8-bit data bus for those functions.

> clock/data processing hardware.  You connect it directly to the cable, as I
...
   recall.  It
otherwise behaves as a uPD765 (i8272). 
Absolutely. The point I was making (not very clearly) is that WD FDC
chips are getting hard to find, but there's no reason not to use an 8272
(or one of the later chips based on this, but with more things integrated
into the device).

But if you insist on 'classic' hardware (meaning all the chips you use
were in production at least 10 years ago), you probably won't be allowed
to use some of these more integrated devices. 

That's exactly the reason I'd prefer to use the WD1002 boards I have around.
They handle both the FDC and HDC functions with a minimum of extraneous
hardware and would, at least in the case of the Z-80 lead to a productive
OS.  That's not as likely in the case of the 6502, since there wasn't much
of use around for it.  Nonetheless, a nonvolatile storage medium of some
sort would be convenient, and if I make the board in question home to both
processors there'll be no doubt about whether one or the other has more or
better resources.  I got these boards in 1982.  When they were brand new
products and, in the case of the 1002's, before they were released
commecially.

...
 -tony 