MESI State Transition Diagram

• BusRd(S) means shared line asserted on BusRd transaction

• Flush’: if cache-to-cache xfers

  • only one cache flushes data

• MOESI protocol: Owned state: exclusive but memory not valid

PrW

r/—

BusRd/Flush

PrRd/

BusRdX/Flush

PrW

r/BusRdX

PrW

r/—

PrRd/—

PrRd/—

BusRd/Flush’

˘

E

M

I

S

PrRd

BusRd(S)

BusRdX/Flush’

˘

BusRdX/Flush

BusRd/

Flush

PrW

r/BusRdX

PrRd/

BusRd (S

)

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