IBM PowerPC 750GX User Manual page 148

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