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IBM PowerPC 750GX and 750GL RISC Microprocessor
gx_03.fm.(1.2)
March 27, 2006
Instruction-Cache and Data-Cache Operation
Page 147 of 377
3.7 MEI State Transactions
Table 3-7 shows MEI state transitions for various operations. Bus operations are described in Table 3-4 on
page 141.
Table 3-7. MEI State Transitions
(Page 1 of 3)
Operation
Cache
Operation
Bus
Sync
WIM
Current
Cache
State
Next
Cache
State
Cache Actions Bus Operation
Load (T = 0) Read No x0x I Same
Cast out of modified block (as
required).
Write-with-kill
Pass 4-beat read to memory queue. Read
Load (T = 0) Read No x0x E,M Same Read data from cache. —
Load (T = 0) Read No x1x I Same
Pass single-beat read to memory
queue.
Read
Load (T = 0) Read No x1x E Same
Pass single-beat read to memory
queue.
Read
Load (T = 0) Read No x1x M Same
Pass single-beat read to memory
queue.
Read
lwarx Read Acts like other reads but bus operation uses special encoding.
Store (T = 0) Write No 00x I Same
Cast out of modified block (if neces-
sary).
Write-with-kill
Pass RWITM to memory queue. RWITM
Store (T = 0) Write No 00x E,M M Write data to cache. —
Store ¦ stwcx.
(T = 0)
Write No 10x I Same
Pass single-beat write to memory
queue.
Write-with-flush
Store ¦ stwcx.
(T = 0)
Write No 10x E Same
Write data to cache. —
Pass single-beat write to memory
queue.
Write-with-flush
Store ¦ stwcx.
(T = 0)
Write No 10x M Same Push block to write queue. Write-with-kill
Store (T = 0)
or stwcx.
Write No x1x I Same
Pass single-beat write to memory
queue.
Write-with-flush
Store (T = 0)
or stwcx.
Write No x1x E Same
Pass single-beat write to memory
queue.
Write-with-flush
Store (T = 0)
or stwcx.
Write No x1x M Same
Pass single-beat write to memory
queue.
Write-with-flush
Push block to write queue Write-with-kill
stwcx.
Conditional
write
If the reserved bit is set, this operation is like other writes except the bus operation uses a special
encoding.
dcbf
Data-cache-
block flush
No xxx
I,E Same Pass flush. Flush
Same I State change only. —
dcbf
Data-cache-
block flush
No xxx M I Push block to write queue. Write-with-kill
Note: Single-beat writes are not snooped in the write queue.