Re: The 6502 is a dynamic CPU, the Z80 is a static one

On Mon, May 4, 2020 at 1:59 PM smf <smf_at_null.net> wrote:
> On 04/05/2020 18:38, Jim Brain wrote:
> > The original NMOS design relies on the fact that the charge on a wire
> > will continue to live there for 300nS or so, as part of the operation
> > of the 6502.  On the 65C02, such things were dumped into flops, to
> > avoid the issue.

Makes sense.

> This may have been the same for the Z80, the CMOS versions are fully
> static but the NMOS ones may not have been.
>
> The original 68000 wasn't fully static either.

The first (and for a while, the only one I knew of) static processor I
encountered was the RCA 1802 (probably-not-coincidentally CMOS).  An
older friend of mine in high school built a Quest Elf and he didn't
own an oscilloscope, so for debugging, he made a debounced one-shot
pushbutton and piped that into the clock input and used an analog VOM
to check various points on the board, cross-referencing with the
timing diagram in the RCA manuals (8 clock ticks per cycle, 1-3 cycles
per instruction).  He did eventually get his board debugged and
switched back to a 1MHz crystal.

-ethan