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Date   : Sun, 28 Sep 2003 19:49:32 +0100 (BST)
From   : Pete Turnbull <pete@...>
Subject: Re: BBC Micro lazy delayed boot! - Interesting develo pment!

On Sep 28, 17:02, Andrew Hancock wrote:
>
> TO TEST only with Acorn 0.9 DFS slightly different problem is
observed. This
> is different to DNFS 1.2, which doesn't display on anything on
screen.
>
> If I substitute the DNFS 1.2 ROM with an original Acorn 0.9DFS eprom,
in any
> socket, with or the 8271 chip installed, the Beeb powers-up
immediately with

> Acorn DFS
> _ flashing cursor and long Beep................................
>
> 15 seconds (faster if warm!)
>
> BASIC appears
> >
>
> same on pressing BREAK and CTRL-BREAK (with Beep.............)
>
>
> Without 8271 installed
>
> BBC Computer 32K
> Acorn DFS
> _ flashing cursor and long Beep................................
>
> same on pressing BREAK and CTRL-BREAK (with Beep.............)
>
> Machine never reports to Basic and sticks.

I find this confusing.  Is all of the above what you get with DFS 0.90?

I'm not surprised it never gets to BASIC.  I'm surprised it does much
at all.  Without the 8271, the NMI will always be active, IIRC.

> I always through the DFS checked for the prescence of 8271 before
mapping
> DFS service rom in memory.

It does.

> If I install both DNFS 1.2 (low priority) and DFS 0.9 (high
priority), I get
> both problems.
[...]
> So total Boot time is 30 seconds. I'm surprised at this because I
would have
> thought as 0.9DFS is at a higher priority it would not map/execute
DNFS 1.2.

Installing both is a really daft thing to do :-)   They're both
checking for the same chip, in the same way (writing and reading
registers, nothing to do with S9 or the NMI) and each finds it, so each
one tries to initialise.  As far as the disk system is concerned,
they're essentially the same software (modulo a few trivial bug fixes
in 1.20).  Neither has a way to say "the disk is all MINE!", only to
say "I see a disk system I can use".

What's the revision of this board?  Early ones (Issue 1,2,3) needed a
small mod to IC27 and S9 to make the NMI work correctly.  The mod *must
not* be made to issue 4 or 7 boards.  Is the Econet NMI link (S2)
fitted (it should be)?  IC27 (a 7438, not a 74LS38) is OK?  Are there
any mods to the board?  Are all the socketed chips OK (it's common to
get a pin bent underneath)?

-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York
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