Building a Z-80 (64bit!!!)

From: Allison J Parent <allisonp_at_world.std.com>
Date: Thu Oct 22 10:14:32 1998

< THe Z180 is already down to 3 cycle/instruction, and the z380 is
< down to 2 cycle/instr. But since the maximum clock rate of the
< 180 is more than 50% higher than the 280, it's the way to go.

No news to me. I'm running a modifed SB180 (z180) and also working with
z280/12.5Mhz. I've looked at z380.

< > of using. I have z80/10mhz parts however and the 2901s would barely d
< > that.
<
< And if you try, most 10 MHz can run at 12 to 14 MHz.

I've taken the 10Mhz part to 12.5Mhz.

<
< > FYI: z80S180s can be had into the 30+ mhz range.
< :) Jep and 1 Meg is still plenty of RAM when running CP/M

That it is.

< But after all where is the sense of having a Z80 as 64 Bit
< processor ? It's a well usable 8/16 Bit processor. Even the
< 380 isnt really an advantage - you just don't realy need this
< 32 Bit instructions. A set consecutive 16 Bit instructions

Larger flat address space. The z380 would make a real good data handler
(z382 is a PC bus slave version for comms) or possibly a graphics
crunchers. Even in the z80 native mode you can access beyond the 64k
basic addressing in a manor that is more convenient than the basic z80
provides. In most cases the extended mode changes the the effect of
the arithmetic overflow in 16bit ops so that 0FFFFh+1 is not 0000. but
10000h. There are of course extended operations as addressing modes
as well.

< can do it in almost the same time. From my point of usage
< a 16 Bit uP is anything you need - compact code, compact data
< and greater over all performance.

Z380 still has those attributes. It saves the memory management overhead
for apps that need to get at spaces larger than 64k.

I plan to do a bit of serious work with one if I can get my hands on a few
and a socket adaptor.

Allison
Received on Thu Oct 22 1998 - 10:14:32 BST