Date   : Mon, 16 Apr 2001 08:00:57 +0100
From   : Mike Tomlinson <mike@...>
Subject: Re: Confusing tube

In article <INEBINJGPKFAHFODGMHCCEBGCBAA.r.gellman@...>,
Richard Gellman <r.gellman@...> writes

>I'm confused about the loading of the Tube OS ROM in the 6502 2nd processor.
>I have two roms download from TBL, one 2K and one 4K.
>
>According the 6502-2nd processor user guide, the tube OS occupies F800-FFFF,
>next to this it says "ROM copied to RAM".

As the second processor has 64k RAM and the maximum addressable space of
the 6502 is 64k, at switch on the tube code is copied from a ROM into
the second processor's RAM.

>On switch-on the tube software is copied from the DNFS ROM in the I/O
>processor to the 4,5,6 and 7 [sic] in the I/O processor.

perhaps it means pages 4,5,6,7 ?  The I/O processor is the BBC itself.
To be honest, I thought the Tube code got loaded at &0D00 so not sure
what is meant here.

>The second processor operating system is copied from a ROM inside the Second
>Processor to &F800-&FFFF.
>
>Now would somebody care to clear this up a bit? :)

for the second processor to work, there has to be code running in both
boxes to allow communication between the two.  It sounds as if you have
downloaded a copy of the 2k second processor ROM from TBL! - not much
use, as it will already be present in any second processor you care to
attach.  Perhaps the 2k ROM is for the 6502 SP and the 4k is for the
Z80?

-- 
"Security-wise, NT is a server with a 'Kick me' sign taped to it."
                      - Peter Gutmann