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User’s Manual
IBM PowerPC 750GX and 750GL RISC Microprocessor
gx_03.fm.(1.2)
March 27, 2006
Instruction-Cache and Data-Cache Operation
Page 143 of 377
the data transactions to memory in order). Note also that all burst writes by the 750GX are performed as
nonglobal, and hence do not normally enable snooping, even for address collision purposes. (Snooping might
still occur for reservation cancelling purposes.)
3.6.4 Snoop Response to 60x Bus Transactions
There are several bus transaction types defined for the 60x bus. The transactions in Table 3-5 correspond to
the transfer type signals TT[0–4], which are described in Section 7.2.4.1, Transfer Type (TT[0–4]), on
page 256.
The 750GX never retries a transaction in which GBL
is not asserted, even if the tags are busy or there is a tag
hit. Reservations are snooped regardless of the state of GBL
.
Table 3-5. Response to Snooped Bus Transactions
(Page 1 of 3)
Snooped Transaction TT[0–4] 750GX Response
Clean block 00000 No action is taken.
Flush block 00100 No action is taken.
SYNC 01000 No action is taken.
Kill block 01100
The kill block operation is an address-only bus transaction initiated when a dcbz or
dcbi instruction is executed.
• If the addressed cache block is in the exclusive (E) state, the cache block is
placed in the invalid (I) state.
• If the addressed cache block is in the modified (M) state, the 750GX asserts
ARTRY
and initiates a push of the modified block out of the cache and the
cache block is placed in the invalid (I) state.
• If the address misses in the cache, no action is taken.
Any reservation associated with the address is canceled.
EIEIO 10000 No action is taken.
External control word write 10100 No action is taken.
TLB invalidate 11000 No action is taken.
External control word read 11100 No action is taken.
lwarx reservation set 00001 No action is taken.
Reserved 00101 —
TLBSYNC 01001 No action is taken.
ICBI 01101 No action is taken.
Reserved 1XX01 —
Write-with-flush 00010
A write-with-flush operation is a single-beat or burst transaction initiated when a
caching-inhibited or write-through store instruction is executed.
• If the addressed cache block is in the exclusive (E) state, the cache block is
placed in the invalid (I) state.
• If the addressed cache block is in the modified (M) state, the 750GX asserts
ARTRY
and initiates a push of the modified block out of the cache, and the
cache block is placed in the invalid (I) state.
• If the address misses in the cache, no action is taken.
Any reservation associated with the address is canceled.