git: 9front

ref: b1a79e9db4d453d99bcf171c57f1734c1c3ebef8
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