Date   : Mon, 09 Oct 2006 22:37:20
From   : Michael Foot <mjfoot@...>
Subject: Re: One more BBC B to fix

In message <4e6fa4f7f2info@...>
          Sprow <info@...> wrote:

> In article <672022E79B6349DBA63CA47178833796@...>,
>    Andrew Chesterton <andrew.chesterton@...> wrote:
> 
> > in the process of loading the OS and is now accessing the wrong
> > locations in the memory map. 
> 
> The OS isn't loaded per se, it's just there. I agree with the general
> suggestion that the address decode is a likely suspect, the OS needs
RAM to
> work everytime it uses a JSR/RTS pair,

I'm still wotking on this problem. So far I've replaced a few ICs with
IC30 (a 74LS74) being one of them. This has helped a bit. Now in 16K mode
I can usually get the machine to boot (bur-beep) but then it locks up
instantly. The screen has the BBC 16K header but the screen then fills up
with BASIC keywords and other junk. Usually it shows STR$ on alternate
lines down the screen. When I press Control-Break I get random charcters on
the mode 7 screen. It still does not boot in 32K mode or with the jumper
off.

I think the general concensus is correct so far. It's either an
addressing issue or a timing one.

I'll keep at it. I becomming a wizz at removing ICs whole without
damaging the board!

Cheers,

Mike.


-- 
Michael Foot <mjfoot(at)paradise(dot)net(dot)nz> *
http://homepages.paradise.net.nz/mjfoot/
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