4-55
BUS OPERATION
When a line is written back, KEN#, WB/WT#, BS8#, and BS16# are ignored, and PWT and PCD
are always low during write-back cycles.
Figure 4-38. Snoop Cycle Invalidating a Modified Line
The next ADS# for a new cycle can occur immediately after the last RDY# or BRDY# of the
write-back cycle. The Write-Back Enhanced IntelDX4 processor does not guarantee a dead clock
between cycles unless the second cycle is a snoop-forced write-back cycle. This allows snoop-
forced write-backs to be backed off (BOFF#) when snooping under AHOLD.
HITM# is guaranteed to remain asserted until the RDY# or BRDY# signals corresponding to the
last doubleword of the write-back cycle is returned. HITM# is de-asserted from the clock edge in
which the last BRDY# or RDY# for the snoop write-back cycle is asserted. The write-back cycle
could be a burst or non-burst cycle. In either case, 16 bytes of data corresponding to the modified
line that has a snoop hit is written back.
242202-150
CLK
AHOLD
EADS#
INV
HITM#
BRDY#
CACHE#
12345678910111213
BLAST#
A31–A4
*
**
A3–A2 0 4 8 C
ADS#
W/R#
To Processor
Write-back from Processor
*
**
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