[f-cpu] usage of 64 registers

[Martin Devera <devik@cdi.cz>]

Hello,

I'm fairly new in this area as I focus mainly on linux
kernel developement.
But this project impressed me and I started to learn more
about it. I've some question and I hope someone can answer
them (and yes I looked archives first to not repeat FAQ).

First during my developement days I never seen algorithm
(except unrolled loops) which can use 64 regs in one stack
frame range.
Why didn't you consider register rotation ala ia-64 which
allows you to simply generate function calls without memory
ops and to do sw pipelining ?
Also I've heard that there are problems with SPARC's register
window usage, can someone clearify it ?

Second question is, how can be the XBar constructed in CMOS ?
Is 4*64 to 4*64 xbar simply 1024 pass-thru gates (N-P mos pair)
plus tree of invertors to accomodate this fanout ?
Or will it consist of latches per port ?

Thanks,
devik

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