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Date   : Mon, 11 Jun 1990 20:16:52 GMT
From   : mcsun!unido!balu!tilmann%cosmo.UUCP@uunet.uu.net (Tilmann Reh)
Subject: Fast Z80?

clldomps@praxis.cs.ruu.nl (Louis van Dompselaar) writes:

> Can anyone tell me if there are any speedy versions of the Z80? 
> (Wasn't there a 280 or something?)

Yes, there was. But I will try to keep order.

There is a CMOS-Z80 available with 10 MHz for some time now, and this spring
they offered a 20 MHz version. As the Z80 peripherals (also CMOS) only speed
up to 10 MHz, this is only of interest if someone uses TTL-only peripherals
(think of embedded control).

The Z180 (or the identical HD 64180) is an upward compatible MPU with at this
time max. 10 MHz clock. However, it is about 25% faster than a 10 MHz Z80,
cause the M1 cycle lasts only 3 clocks (instead of 4). The MPU contains two
UARTs, two 16-bit-Timer/Counters, two DMA controllers, and a simple banked
MMU for 1 MB addressing space. Bus size still 8 bits. Adds a few instructions
to the Z80 command set (non-destructive AND, and 8x8 bit unsigned multiply).

Z280 is the latest offspring of Zilog's 8-Bit crew. It is also Z80 compatible
but not Z180 compatible. Clock frequency 10 MHz (standard), will go in
quantities with 12.5 MHz in 3Q90. It has a pipelined CPU so speed comparison
depends on the application. With standard CP/M programs, it is a little bit
faster than the Z180 at the same clock (using 16-bit bus). This MPU contains
only one UART, three 16-bit-T/C's, four DMA-controllers, a 256-byte cache,
and a complex paged MMU for 16 MB. It can be configured for 8-bit-Z80-Bus mode,
or for 16-bit-Z-Bus mode (the Z8000 bus). Instruction set is about twice as
big as that of Z80, the new instructions include signed & unsigned multiply
& divide for bytes & words, and very powerful new addressing modes (base index,
register index, for example). It also supports System and User Modes, with
different MMU pages and different privileges.

Both Z180 and Z280 have programmable bus timing (wait state generators), but
the Z280 is the more flexible one.

As a plug-in replacement for the Z80, neither of them is useable. But, you
could adapt them both via some little PCB. Both MPU's are housed in PLCC-68
cases, the Z180 is also available in 64-pin shrink dip. Of course if you do
that, the Z280 cannot be driven in Z-Bus mode.

Perhaps you simply contact Zilog and let them send you some data sheets.

However, if you are interested in a new computer system with the Z280,
please contact me (as I just finished design of my single-board Z280 computer).

Tilmann Reh

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