Date   : Sat, 23 Sep 2006 12:24:11 +0100
From   : jgh@... (Jonathan Graham Harston)
Subject: Re: 6502Tube emulator in BASIC

>Message-ID: <4e67218bd9info@...>
 
Sprow <info@...> wrote:
>    Jonathan Graham Harston <jgh@...> wrote:
> > As a proof of concept I put together a 6502 emulator last night,
> > written in BBC BASIC, starting with PDPTube and replacing the CPU
> > components. See http://mdfs.net/Apps/Emulators/Tube/65TubeEm/65Em
> 
> Cor- it works too!
> 
> Interestingly (not a complaint!) many other operations give "No room", even
> though HIMEM, LOMEM, TOP, PAGE all look right. Even just
>  P%=1
 
Could be because CPY and CPX were actually doing CMP, or ROL that
tried to store a 9-bit value into a byte. I've just checked the
current version and it's happy with var=val.
 
I left it running ClockSp for quite some time and it told me it
was running at the equivalent of 0.00MHz !
 
> A most impressive piece of software, I look forward to seeing how it
> progresses,
 
The progression will be either to build the "harness" that Acorn's
65Tube needs to work, or write a ARM 6502Tube from scratch. I've
been looking through Z80Tube to see what it needs to work.
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
The most perfect world is an imperfect world as the imperfections give
people a reason to strive to change it.