Bug#72479: Data Access Exception

[Alan Bain <A.F.R.Bain@statslab.cam.ac.uk>]

Hunting through some dusty sun hardware manuals reminds me of the
following which may be causing my problem.

In the IPX there are 4 memory banks which can hold either a 
1Mb (silly!), 4Mb, 8Mb or 16Mb SIMM (72 pin parity).  The memory
is not contiguous and each block is mapped onto a 16Mb boundary,
creating memory gaps.  The IPX which wont boot has 4 8Mb SIMMs making
non-contiguous memory.

My IPX which boots OK has one 16MB SIMM. Thus 0-16Mb is a contiguous
block.  

Maybe there is an erroneous hardcoded address which the RAMdisk
runs into by using direct physical memory access instead of 
going through the MMU allocation procedures.


Alan Bain