Re: Re: Re: Re: Disk rom dump (D9090)

From: Marko Mäkelä <>
Date: Wed, 5 Feb 2014 22:54:00 +0200
Message-ID: <20140205205400.GA4039@x220>
On Wed, Feb 05, 2014 at 09:14:46PM +0100, wrote:
>   - From 023D to 03FB : Filled with AA (NOPs ?)

TAX. I remember seeing this fill pattern in the Commodore 64 ROM too.  
It is 10101010 in binary.

Speaking of firmware, my 10-year-old son recently started reading a 6502 
machine language book from the 1980s. When I debugged a program with him 
in VICE (it was a simple checksum program for finding simple mistakes 
when typing in BASIC listings by the publisher), I noticed that the 
Commodore 64 firmware contains the constant 88 instead of 80 as the 
logical line length. I guess that they forgot to adjust that from the 
Commodore VIC-20 ROM. On the Vic, the logical line is up to 4 physical 
lines (4*22=88), while on the 64, the maximum is 2*40.


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Received on 2014-02-05 21:00:02

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