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In a message dated 20-Jul-98 15:56:16
James Youngman <JYoungman@vggas.com> wrote:
>>>>>> "ts" == Tomaz Stih <tomaz.stih@triglif.com> writes:
ts>> When dealing with 68000 boards with no vector base register
ts>> there is a problem with setting vectors because it is common
ts>> to put ROM at 0x0000 address where vectors reside thus making
ts>> it impossible to change them.
>00000000 does not have to be ROM. You just have to be able to load 8
>bytes from it at reset time. I've seen boards by Pro-Active Control
>which use a counter to change the memory mapping after the right
>number of bus cycles to that the vectors can be in RAM (except,
>effectively, the reset vector).
An "interesting" note might be that (M68K) Amiga-computers has RAM at address
0, still they do bootstrap from ROM ;-}
I don't know *how* the hardware (RAM/ROM switch) is implemented, though.
,-.
,-. / \
/ \ / \
/Hannu E K Nevalainen ,-.
' www.it.kth.se/~henk \ / `-* _ // 1985+
`-' `-' \X/Amiga user
Personal rc5-stats: 6,717 2^28-key blks, i.e. 1,803,080+ Mkeys, M68K Amiga.
--
The complete Amiga memory map: AbsExecBase == 4L