Re: [Milkymist-devel] [Milkymist port] virtual memory management

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

> Indeed the MMU does not have support for Address Space ID [...]

> Moreover, adding new instructions is not that simple and I would
> prefer using the less possible resources for the MMU and save the
> very small amount of unused opcodes for other projects.

This _can_ be done without needing additional instructions.  For
example, you could have three MMU registers: one holds an ASID and
maybe an access size indication, one holds an address, and one holds
data.  To read/write some other ASID, you stuff the ASID in the first
register, the address in the second, and then read/write the third.
I'm sure there are lots of other possible designs.

It may be better to do it with special-purpose opcodes (eg the SPARC's
ld*a and st*a instructions), but it is by no means necessary.

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