Subject: Re: None
To: None <amiga@NetBSD.ORG>
From: Michael van Elst <>
List: amiga
Date: 12/05/1995 02:41:24
Jukka Marin <> writes:

>The trick of using two 68000's had to be used to get around the exception
>limitation.  I can't recall the details, but the only way I can think of
>is to run one CPU behind the other.  When the first one encounters a bus
>error (or anything that requires swapping data from disk to RAM), the
>condition is handled and then the second CPU runs the instruction that
>caused the exception.  Or something like that. :-)

The trick is to NOT cause an exception. Instead the page faulting
CPU is frozen while waiting for the bus cycle to complete. The
second CPU fetches the page from secondary storage and then tells
the bus logic to ask the first CPU to continue or to rerun the bus

                                Michael van Elst

                                "A potential Snark may lurk in every tree."