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User’s Manual
IBM PowerPC 750GX and 750GL RISC Microprocessor
Instruction-Cache and Data-Cache Operation
Page 148 of 377
gx_03.fm.(1.2)
March 27, 2006
dcbst
Data-cache-
block store
No xxx
I,E Same
dcbst. —
Pass clean. Clean
Same Same No action. —
dcbst
Data-cache-
block store
No xxx M E Push block to write queue. Write-with-kill
dcbz
Data-cache-
block set to
zero
No x1x x x Alignment trap. —
dcbz
Data-cache-
block set to
zero
No 10x x x Alignment trap. —
dcbz
Data-cache-
block set to
zero
Yes 00x
ISame
Cast out of modified block. Write-with-kill
Pass kill. Kill
Same M Clear block. —
dcbz
Data-cache-
block set to
zero
No 00x E,M M Clear block. —
dcbt
Data-cache-
block touch
No x1x I Same
Pass single-beat read to memory
queue.
Read
dcbt
Data-cache-
block touch
No x1x M I Push block to write queue. Write-with-kill
dcbt
Data-cache-
block touch
No x0x I Same
Cast out of modified block (as
required).
Write-with-kill
Pass 4-beat read to memory queue. Read
dcbt
Data-cache-
block touch
No x0x E,M Same No action. —
Single-beat read Reload dump 1 No xxx I Same Forward data_in. —
4-beat read (dou-
ble-word-aligned)
Reload dump No xxx I E Write data_in to cache. —
4-beat write (dou-
ble-word-aligned)
Reload dump No xxx I M Write data_in to cache. —
E
→I
Snoop
write or kill
No xxx E I State change only (committed). —
M
→I
Snoop
kill
No xxx M I State change only (committed). —
Push
M
→I
Snoop
flush
No xxx M I Conditionally push. Write-with-kill
Push
M
→E
Snoop
clean
No xxx M E Conditionally push. Write-with-kill
Table 3-7. MEI State Transitions (Page 2 of 3)
Operation
Cache
Operation
Bus
Sync
WIM
Current
Cache
State
Next
Cache
State
Cache Actions Bus Operation
Note: Single-beat writes are not snooped in the write queue.