More thoughts on building a Z-80 (64bit!!!)

From: Arfon Gryffydd <ArfonRG_at_DIEspammerSCUM.Texas.Net>
Date: Thu Oct 22 19:08:03 1998

>Where are you storing Register A and B? If inside a controller, then
>only that controller has access to them, if you're using ECL latches then
>you're going to have to make virtually the entire data path outside the
>microcontrollers

DING DING DING!!!!! Give that man a cupie doll!!!

My concept:


 ______ ___ ______ ___ ______ ___
| u |=| |=| u |=| |=| |=| |=
| - |=| m|=| - |=| m|=| |=| |=
| c |=| e|=| c |=| e|=| |=| |=
| o |=| m|=| o |=| m|=| |=| |=
| n |=| |=| n |=| |=| |=| |=
|______| =|__|=|______|=|__| =|_____ |=|__|=

etc...

>Actually, for prototyping wire-wrap is a lot faster to do, and it'll
>clock faster as well. It's much easier to get a good ground plane on a
>wire-wrapped board than a double-sided PCB
>
>> A little laser-printer transfer plastic and an exacto-knife.
>
>You do realise that to get anything like the clock rates you want (or
>even a tenth of them) you have to treat the tracks as striplines. This
>means the width of the PCB track is critical. Toner transfer may not be
>good enough.

I know that Track get very touchy at 900Mcyc speeds but, I also knew that
it was near impossible for me to find something like what I wanted at those
speeds.... Plus, Half the fun of building stuff is learning what will and
will not work and then MAKING IT WORK!!! (Pass the hammer please)


>> As for the Z-80 vs Alpha features.... I like:
>>
>> 1) I/O ports. I hate the memory map stuff. (yes, I know it is the way
>> things are done now)
>>
>> 0000H - A100H System
>> A200H - C200H Video
>> DA00H - DAFFH IDE HD 1
>>
>> That sucks (in my opinion). (You like my 16bit addressing? kinda make you
>
>Why? The idea of having one set of instructions to access both memory and
>I/O is actually very nice. Of course having an MMU so you can map out the
>I/O and have an entire address space of RAM if you want it makes things
>even nicer.

Except when it comes to interfacing hardware..... You ask yourself....
Is there a memory chip at this location??? Where was that darned memory
break anyway??? To hell with that... memory in memory locations... I/O
in I/O locations.... otherwise cats and dogs will be mixing and god forbid
that that happen. Seriously, when writing in assembler..... It's nice
to see a I/O op code to help me keep straight that this is an I/O
operation....


>> Your response: "But, what if you need to transfer a big block of data like
>> a NIC? You really need to memory map that."
>>
>> My answer: "Pretend that the IO addresses are memory. With a 128 bit
>> address bus, you'll never run out of spaces!"
>
>So what you really want is an I/O page and an addressing mode (a bit like
>Direct Page on the 6809) that accesses the I/O ports. And also allows
>them to be accessed by normal memory reference instructions.

You know, that is exactly how I see I/O addresses..... That mem/IO pin as
a 17th address bit (except 0000H I/O is not sequentially accessable from
the address registers when you hit the end of your instruction memory)

Note: on the Model II (TRS-80) there was an option to use page the memory
so you could get more than 64K in the thing.... If I remember, it used a
Z-80 I/O address as the pager.

Damnit! I want a 64bit Model II !!!!!!!! (Running and 500Gcyc of-course).
With 8" Laser-Optical drives... and OH OH!!! I want a Thomas-Conrad
100Mbps Fiber ARCnet to connect it to my Linux machines!!!!
Oh.... and a Dodge Viper (just so I'll be secure in my manly-ness).

Arfon



"Programming today is a race between software engineers striving to build
bigger and better idiot-proof programs, and the Universe trying to produce
bigger and better idiots. So far, the Universe is winning." -- Rich Cook
Received on Thu Oct 22 1998 - 19:08:03 BST