Xref: utzoo comp.os.os9:434 comp.sys.m6809:1054
Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!sharkey!aucis!easton
From: easton@aucis.UUCP (Jeff Easton)
Newsgroups: comp.os.os9,comp.sys.m6809
Subject: Re: Adapting coco OS9 to other systems
Summary: We're getting close...
Keywords: OS9, coco III, uniboard
Message-ID: <391@aucis.UUCP>
Date: 28 Mar 89 00:51:19 GMT
References: <386@aucis.UUCP> <989@mcrware.UUCP> <388@aucis.UUCP> <992@mcrware.UUCP>
Organization: Andrews University, Berrien Springs, MI
Lines: 38


> Tim Koonce writes:
>
>The big hassle with getting it running will be interrupts.  The CoCo
>interrupts are fairly bizarre.  Time-slicing works off of a 60hz timer
>driven by the video circuitry.  Some interrupts are wired as FIRQ,
>rather than IRQ, which is what OS9 was originally designed to use,
>and the CoCo OS9 kernel has some code to hack an FIRQ stack frame
>into an IRQ stack frame for compatibility with the rest.
 
Hmmm,  My 6522 has two 16 bit timers.  With a E clock at 2 Mhz, /65535 
yielding a maximum of 30.5 Hz or 32.8 mSec between IRQ's (not the FIRQ).
so far, so good...
 
>As for Level 1 that Tandy is selling, their Level 1 off the shelf is
>ver. 1.2, which won't run on the CoCo 3 as-is, due to some additional
>memory restrictions on the CoCo3.  However, there's an upgrade for
>$25 to ver. 2.0, which does run on the CoCo 3 just fine.  It might
>actually be easiest to pick up a CoCo 1 or CoCo 2 at a flea market
>used, and work with that.  Be a lot cheaper, certainly.
 
Okay, but does version 2.0 (not level II) buy me anything?  Is it a bug
fix release?  Will 2.0 run on a coco 1 or 2? (assuming I scrap up a coco 1
or 2 to port it on).  I would like to get the best version possible.
 
One other question, do I need DMA for the disk transfers?  My board has
a 6844 DMA chip but I confess, I've never used it.
 
>Hope this helps.
 
A big step in the right direction.
 
>
>                                        - Tim Koonce
 
	Jeff Easton
	Zenith Data Systems