Ahold-Initiated Inquire Hit To Modified Line - AMD K5 Technical Reference Manual

AMD-K5 Processor Technical Reference Manual
AHOLD-Initiated
Inquire Hit to
Modified Line
5-160
Figure 5-11 shows the same sequence as in Figure 5-10, but this
time the inquire cycle hits a modified line. As in Figure 5-10,
system logic asserts INV with EADS. Two clocks later, the pro-
cessor asserts both HIT and HITM. A few clocks later the pro-
cessor drives a writeback for the cache line and then
invalidates its cached copy. The processor holds HITM
asserted until one clock after the last BRDY of the writeback.
If system logic holds AHOLD asserted throughout an inquire
cycle and any required writeback, system logic must latch the
inquire cycle address when it asserts EADS. This is required so
that, if the inquire cycle hits a modified line, the address used
for the writeback need not be driven by the processor when
the processor asserts ADS for the writeback. Instead, A31–A5
remains an input-only bus and system logic must use its
latched copy of the inquire cycle address. By contrast, if sys-
tem logic always negates AHOLD before the writeback, the
processor drives the writeback address when it asserts ADS for
the writeback, and system logic need not retain a copy of the
inquire cycle address. While the processor drives the write-
back address, it drives only the beginning address for the 32-
byte transfer on A31–A5. System logic must determine the
remaining addresses as shown in Table 5-21 on page 5-150.
18524C/0—Nov1996
Bus Interface