git: 9front

ref: 685e107f4e4571c15c19f580590f5c683e6fa70c
dir: /sys/src/cmd/qi/timing/

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units
	branch
	integer
	floating point
on 601
	issue at most one per unit per cycle
	eight entry instruction queue
	can fill queue from cache in one clock cycle
		loads from requested address to end of cache block
pipeline
	prefetch
		includes ins. cache access cycles
	decode
	execute
	writeback

fpu
	IQ[3210] → fpu buffer/decode [≥1 cycle] → execute 1 → execute 2 → writeback
iu
	IQ0/decode → buffer [if exec busy] → execute [hold for dependency] →
					circulate in load/store
					writeback
bpu
	IQ[3210] → decode/execute → writeback

notes
	address calculation must complete before stored value enters write buffer