🚀 go-pugleaf

in article <8908181206.AA07159@jade.berkeley.edu>, U211344@HNYKUN11.BITNET (Olaf 'Rhialto' Seibert) says:

> This makes me wonder. The 2000 doesn't need a boot rom, does it? The
> start of the kickstart ROM has the same structure as the boot rom
> in the 1000. (I know; I disassembled it). Does the OVL line maybe
> map a PART of the kickstart rom to location zero? 

In fact.  The base of the ROM ($00FC0000) is overlaid at location 0 when the
OVL line is asserted.  The same thing happens in A1000s; this overlay tells the
system where the start of code is, in standard 68000 fashion.  One interesting
side effect of this ROM overlay, plus the way autoconfig works, is a noticable
lack of RAM after RESET.  Most of the time that's not a problem, but if you
ever need to write a program that resets the machine and then does something
other than jump to the start of ROM, it's a problem.  I'd personally be 
interested in seeing a routine that would reliably do that on a 68000 machine;
I don't think it's possible....


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> [E.A. Poe, 1844]                           U211344@hnykun11.bitnet
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