Re: 6809 / 6702 puzzle

Date: Thu, 10 May 2012 19:52:13 +0200
Message-ID: <5435669.72151336672333792.JavaMail.www@wwinf3703>
Glad you found the document useful. My motto is that the job's not done until you've written it up!
Yes. That was how we started by returning or nop-ing out the subroutines. The callers of the subroutines inspect the register values that are returned and misbehave if they are incorrect. When we faked the 6702 check subroutine we then found this nasty checksum routine. You don't really know that is there until you try to edit a source program within one of the langauges (e.g. Pascal) - it won't let you! The patch for the 6702 access subroutine basically fakes the register return values. Technically - I could have done the same with the checksum subroutine - but it was easier to make the checksum right (a one byte patch) rather than patch it out (more than a one byte patch).
> Message Received: May 10 2012, 05:58 AM
> From: "William Levak" 
> To:
> Cc: 
> Subject: Re: 6809 / 6702 puzzle
> On Mon, 30 Apr 2012, wrote:
> > I have just finished my write-up and will e-mail it to Mike later on today
> so that he can include it on his web page along with the disk
> > images.
> >
> > This document should tell you how to run all the hd (Hello Dave) programs for
> the different languages and what results to expect (as most
> > of the Waterloo languages just misbehave if the 6702 check passes but the
> checksum routine for the 6702 sub-routine is incorrect). It will
> > also tell you how we identified what byte sequence to add into VICE to make
> it work with the original disks - and how I identified the
> > patches to make to the Waterloo disks. if anyone wants to do the same on the
> V1 Waterloo disks - or on a different disk image - this
> > document should tell them what to do.
> Good write up. I found it much easier to follow than the collection of 
> e-mails.
> You describe three routines associated with the copy protection:
> 6702 access
> sumcheck
> "suicide" routine
> Have you tried just NO-OPing out these routines?
> SDF Public Access UNIX System -
> Message was sent through the cbm-hackers mailing list

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Received on 2012-05-10 18:00:14

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