Freescale Semiconductor PowerPC e500 Core, Reference Manual

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Core Complex Overview
PowerPC e500 Core Family Reference Manual, Rev. 1
Freescale Semiconductor 1-9
Figure 1-4. Three-Stage Load/Store Unit
— The three-entry data line fill buffer (five-entry on the e500v2) is used for loads and
cacheable stores. Stores are allocated here so loads can access data from the store
immediately.
— The data write buffer contains three entries: one dedicated for snoop pushes, one
dedicated for castouts, and one that can be used for snoop pushes or cast outs.
• Cache coherency
— Supports four-state cache coherency: modified-exclusive, exclusive, shared, and invalid
(MESI). Note, however that shared state may not be accessible in some
implementations.
— Bus support for hardware-enforced coherency (bus snooping)
• Core complex bus (CCB)—internal bus
— High-speed, on-chip local bus with data tagging
— 32-bit address bus
— Address protocol with address pipelining and retry/copyback derived from bus used by
previous generations of PowerPC processors (referred to as the 60x bus)
— Two general-purpose read data buses and one write data bus
• Extended exception handling
— Supports Book E interrupt model
– Less than 10-cycle interrupt latency
– Interrupt vector prefix register (IVPR)
Reservation
Station
Load/Store Unit
(64-/32-Bit)
Load
Data Line
Fill Buffer
Data Write
Buffer
L1 Store
Queue Miss
Queue
To core interface unit
To data cache
To GPR operand bus
To completion queue
To GPRs
Three-Stage Pipeline
Queues and Buffers
e500v2 (9 entry)
e500v1 (3 entry)
e500v2 (5 entry)
e500v1 (4 entry)