Date   : Thu, 16 Aug 2007 13:45:04 +0200
From   : robert@... (Robert Schmidt-Cisternas)
Subject: Acquired Beeb with symptoms...

Thanks:
I swapped the two 6522s, with no apparent change.  You say "temporarily"
- they shouldn't differ in any way, should they?
I haven't been able to locate any shorts.

The machine came with a spare Norwegian OS (Norwegian characters in mode
7), but using it makes no difference either.

Cheers,
Robert


-----Original Message-----
From: bbc-micro-bounces+robert=schmidt-cisternas.net@...
[mailto:bbc-micro-bounces+robert=schmidt-cisternas.net@...
k] On Behalf Of Sprow
Sent: 16. august 2007 08:40
To: bbc-micro@...
Subject: Re: [BBC-Micro] Acquired Beeb with symptoms...

In article <D27938D1A467B04B9D1B16361BA84C970182A8@...>,
   Robert Schmidt-Cisternas <robert@...> wrote:
> I just acquired a Beeb (I haven't owned one since 1986 :-)), and was
> wondering if the following symptoms ring any bells:
>
> - Pressing BREAK once seems to freeze the machine
> - Pressing BREAK a second time seems equivalent to Ctrl+BREAK (or
> power-on?)
> - In general the machine seems sluggish, especially in graphics modes
-
> it is not noticeable when typing, but games run much slower than I
> remember them.  For example, the original Repton scrolls at about 2
> frames per second(!)

Sounds like it's spending a lot of time servicing interrupts which
aren't
really there. There's a project to do this deliberatly at
 http://www.sprow.co.uk/bbc/buildit.htm
but you don't want this behaviour!

My best bet on no other information would be something wrong with the
system
via or decoding of the slow bus nearby. The system via is heavily
involved
in interrupts from sources which might not really be there (light pen
for
example), it determines whether the last reset was a power on or not,
and
also runs some timers.

Try swapping it with the user via temporarily. Also maybe take out the
whole
motherboard to check for shorts (washers/paper clips etc) trapped
underneath?
Sprow.


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