🚀 go-pugleaf

In article <AGLEW.90Jan31211451@dwarfs.csg.uiuc.edu> aglew@dwarfs.csg.uiuc.edu (Andy Glew) writes:
>>Having a microcoded unaligned data capability is faster than
>>user-level instructions doing the same thing.
>
>Why?
>
>Microcoded unaligned data takes two cycles to load an unaligned datum.
>(Assuming the unaligned datum overlaps two data bus widths.)  MIPSco
>style load-left and load-right take two cycles to load the same
>unaligned datum.


I was thinking of bus-wide words (i.e., typically 32-bits).
You have at least:
     BUS FETCH / SHIFT ALIGN / BUS FETCH / SHIFT ALIGN / OR / STORE
Implementing these at typical user level adds even more -- tests to
figure out how much to shift etc.


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Phil Ronzone   Manager Secure UNIX           pkr@sgi.COM   {decwrl,sun}!sgi!pkr
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