Re: Z80 type differences?

[et472@FreeNet.Carleton.CA (Michael Black)]

"Tristan Mumford" (nintendologist@nospam.gmail.nospam.com) writes:
> G'day.
> 
> I have a question that I haven't been able to answer easily. The question
> is based on a problem I have.
> 
> My poor Apple//e Platimum's Z80 card is dead. Trying to use it locks it
> instantly. This is due to a smeared cap that shorted a couple of lines. I
> replaced the offending capacitor. There was no damage to the apple.
> 
> However the card is still dead. Thankfully it's the standard Z80 Soft
> card. And everything is standard and socketed.
> First step I'm going to replace all the glue logic chips. If that doesn't
> do it there's the Z80B.
> It's the only Z80B I have. I have a stack of Z80A MPUs. And there are
> Z80-CTC MPUs on eBay. What's the difference and which can be used with the
> least modification, if at all?

The "A" and the "B" should denote the speed the CPU can run at.  That was
the case with other 8bit CPUs, and I'm pretty certain that applies to
the Z80.  The reference I have handy came out too early to list such
details, though.

My guess would be the "B" can run faster than the "A", but that might
not be relevant in the Z80 card where the maximum may not be hit.

Zilog tended to use odd number schemes.  In the fine print there'd
be something like a five digit number for each part, but more prominently
would be something like that "Z80-CTC" which wouldn't be a CPU, but
an IC in the Z80 family, and I'm thinking that's a timer.  This is
opposed to the Motorola scheme, where the timer in the 6800 family
would be the 6840, which can't be mistaken for something else.

Someone with a more up to date source will hopefully reinforce
all this, but that CTC just seems so unlikely I wouldn't want
you to order one with the expectation that it's a CPU.

  Michael