final example:

A=B+C
D=E-F

program to implement this example:
LDB $201
LDC $202
ADDABC; A=B+C
STA $200; save result
LDE $204
LDF $205
SUBDEF; D=E-F
STD $203
; see if you can re-arrange to avoid data hazards.

answer:
LDB $201
LDC $202
LDE $204; avoid a data hazard stall
ADDABC
LDF $205; was exchanged with below to avoid data hazard stall
STA $200; was exchanged with below to avoid data hazard stall
SUBDEF
; do something else to give D time to "exist"
STD $203

by scheduling the instructions, the compiler attempts to produce code for which there is one instruction per clock tick (per execution unit).

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speedups and parallelism in programs there are many approaches to increasing the number of instructions microprocessors can do per clock tick.