Re: 1541 ROM areas recognition

From: silverdr_at_wfmh.org.pl
Date: Thu, 7 Nov 2013 15:20:12 +0100
Message-Id: <AB443E66-EEC3-4D46-91A7-163A78FB95FD@wfmh.org.pl>
On 2013-11-07, at 00:39, Groepaz wrote:

>>>> Is there a reliable, software way of recognising ROM areas of a 1541
>>>> (all models)? I mean without knowing what kind of ROM is actually
>>>> installed. I assume that all of them have to cover up to the end of
>>>> 6502 address space (if not for anything else then at least due to h/w
>>>> vectors) but what about the starting point(s) and what if there happen
>>>> to be some non-contiguous chunks?
>>> 
>>> not sure if i understand the question correctly.... but to find out if
>>> there is rom or ram at a certain address, write to it and see if the
>>> value changed? (backup/restore the original value ofcourse)
>> 
>> Well, finding RAM would be as easy as you wrote. What is needed though is
>> to distinguish ROM from all other (than ROM) types of things that may
>> dangle around the corners of address space. Not only RAM. Those may be RAM
>> but also e.g. port chips, gaps, unconnected address ranges..
> 
> it would be easier to give an advice if you'd tell what exactly you are trying 
> to do....

NP - I once wrote a simple drive-ROM dumper program, which works fine as long as I modify it every time a different ROM layout pops up.  Which is of course that I need to know the layout in advance. Which means either knowing what's inside or opening, checking, analysing, ... I am thinking (wishfully - probably) of making the program universal in the sense that it could detect ROM areas itself.

> I have only ever needed something like that to find out how much RAM 
> is installed in the drive and where it is located - all other info is known 
> anyway (like location of i/o chips).

Not really. DD3 equipped 1541 is a good example of a situation when this does not hold true. It has different I/O location (the parallel port PIA), different RAM size/location and different ROM size/location.

-- 
SD!


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Received on 2013-11-07 15:00:05

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