Out-of-Order Execution

⚙ machine
Preset
⊞ panels
The ROB, map table, free list, CDB and reservation stations are always shown.
cycle 0 / 0
⚙ view
Layout

Reorder buffer

ROB
ht#Insn TToldSXC

Map table

Map Table
RegTrdy

CDB common data bus

CDB
T

Free list oldest first

Free List

Reservation stations

Reservation Stations
#busyopTT1rdyT2rdy
Below: the pipeline diagram and the event log track the run; they are not hardware, and nothing in the datapath above is wired to them.

Pipeline diagram

What happened this cycle

    Dependences

    Only the RAW (true) dependences are drawn: renaming removes the rest. An instruction sits one step to the right of the last value it waits for; instructions stacked in one column wait for nothing from each other and could all run at once. Tall and narrow: plenty of parallelism. Long and flat: a chain that no machine can shorten.