Date   : Fri, 02 Jan 2009 00:01:55 +0000
From   : splodge@... (Richard Gellman)
Subject: Master Turbo ROM dump?

Hi,

There's a reason why a "grab" of the ROM won't work. On startup, the 
TUBE ROM is copied from ROM to RAM (an interesting latch circuit deals 
with this, and gets disabled on the first I/O access). The ROM then does 
some initialisation and then overwrites the unneeded TUBE ROM sections 
with data. Thus, the memory space no longer contains the proper TUBE ROM.

Incidentally, its copied from ROM to RAM to maximise the amount of RAM 
available for applications. You can even completely overwrite the 
provided TUBE routines and supply your own to get more space or maximise 
execution efficiency. I believe Elite does this in the TUBE version.

-- Richard


Michael Firth wrote:
> Does anyone have a working copy of the Master Turbo ROM available online?
>  
> I found one on the MDFS pages, but I suspect it may have been dumped 
> from a running Turbo (it seems to have values in the I/O space), 
> rather than being a straight dump of the ROM.
>  
> Certainly, swapping it for the standard 6502 Co-Pro image in BeebEm 
> doesn't work, which I would expect it to, given that I believe the 
> hardware is very similar
>  
> Thanks
>  
> Michael
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