Date   : Wed, 10 Oct 2012 07:52:27 +0200
From   : kortink@... (John Kortink)
Subject: Master booting itself

On Tue, 09 Oct 2012 23:11:45 +0100, "J.G.Harston" <jgh@...>
wrote:

>An oddity with my Master 128 that started a few days ago.
>
>Pressing Ctrl-Break boots, even though configured to NoBoot. It's
>not a keyboard fault as Ctrl-Shift-Break doesn't boot, so Shift
>is correctly reversing the boot status. Even odder, it sometimes
>doesn't happen. About one in nine or ten Ctrl-Breaks it doesn't
>boot.
>
>OSBYTE 255 is being set to b3=0 (ie, do a boot) by the Ctrl-Break,
>even though configured to NoBoot. I've tried with all ROMs unplugged
>and it still does it - trying to boot from tape - so it doesn't appear
>to be a ROM changing OSBYTE 255 on startup. I've tried wiping the CMOS
>settings and reloading them, but that hasn't changed anything.
>
>Anybody else seen this occuring? Another thought was maybe something in
>the time is overflowing and a presumed Carry Clear is becoming Carry 
>Set
>somewhere (or vis versa), though I set the clock back to last year and
>that didn't change anything.

Clearly one of the crossbeams gone out o'skew on treadle.

More things to do : check OS ROM contents, check RAM, check
slow databus ...


John Kortink

-- 

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