[Coco] Color basic 1.0, 1.2 differences.
robert.gault at worldnet.att.net
Sat Jan 20 23:37:53 EST 2007
Phill Harvey-Smith wrote:
> Ahh, but I was talking about plain non-extended color basic, version
> 1.0, which seems in software to only detect 4K or 16K rams. Do you know
> what version of Color basic is in there ?
The ROM is Color Basic 1.1 in my F-board Coco1. Looking at the source
code for the 1.0 ROM, it reads a PIA at $A057 to determine 4 or 16K of
RAM and sets the SAM at$A06A for 16K. However, at $A0AB the ROM has a
routine which looks for the top of RAM by testing memory. It stops when
memory can't be changed. I'm not sure what would happen if 32K or more
of RAM was present, the SAM set for 16K, and data stored above $4000.
All you need to do manually if more than 16K RAM is present would be to
STA $FFDD, STA $FFDA after the initial boot is complete. That will
indicate 64K dynamic RAM. This could easily be put in a modified disk
ROM or entered from the keyboard.
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