Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!killer!bobc
From: bobc@killer.DALLAS.TX.US (Bob Calbridge)
Newsgroups: comp.sys.cbm
Subject: Re: Questions about 128 Reliability (Considering upgrade from C64)
Summary: yeah, it do
Message-ID: <5745@killer.DALLAS.TX.US>
Date: 8 Oct 88 03:08:38 GMT
References: <205.234963B0@isishq.FIDONET.ORG> <39729@yale-celray.yale.UUCP> <10342@s.ms.uky.edu>
Organization: The Unix(R) Connection, Dallas, Texas
Lines: 17

In article <10342@s.ms.uky.edu>, simon@ms.uky.edu (Simon Gales) writes:
> In article <39729@yale-celray.yale.UUCP> sekora-jay@CS.YALE.EDU (Jay Sekora) writes:
> >In article <205.234963B0@isishq.FIDONET.ORG> Geoffrey.Welsh@isishq.FIDONET.ORG (Geoffrey Welsh) writes:
[Correspondence deleted]

> The Z80 in the 128 DOES use the 8502 for its i/o, although I am not
> quite sure why.  The Z80 seems to be able to access all of hardware (or
> can it?), is using the 8502 faster?  Maybe they did it to keep the
> cp/m kernal (?) smaller...?   The Z80 is in control on power up, it is
> the one that decides whether to go into cp/m or cbm mode.
> 							Simon.

You're correct.  The Z-80 is capable of accessing all the Commodore registers.
I've written a music program that uses the SID chip registers.  The trick is 
to load the BC register pair of the Z-80 with the address of the register you
want to access and evoke the INP or the OUTP code to get the contents of that
register into the accumulator.