On Mon, 23 Mar 1998, Allison J Parent wrote:

> <A second ball of hair is the J-11. If you have a full 4Mb, you can
> <address the last 8K as instruction without frobbing BSS7. Only
> <D-space references assert BSS7, or sould I say, only references
> <reloceated by D-space PAR/PDRs assert BSS7. This is usefull,
> <a it give you another 4kw of instuctions for your driver!
> <Does nothing for data or poll space alas.
> 
> This is where the "system" has to be written defensively and any device 
> probes done before turning on the mapping hardware.  It likely applies 
> to 11/70s and possibly VAX via UBAs (or the qbus equivilent) as well.

While slightly off-topic, the 11/70 don't do it like that. Instead, you
can actually run programs off CSR space. At least one diagnostics toggled
in by hand is located in the PAR registers of the MMU while the MMU is
off. This is very handy if your memory isn't working. :-)


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