AMD-K6 AMD [Advanced Micro Devices], AMD-K6 Datasheet - Page 200

• Manufacturer Part Number: AMD-K6
• Description: AMD-K6 Processor
• Manufacturer: AMD [Advanced Micro Devices]

AMD-K6
8.9
Table 30. Data Cache States for Read and Write Accesses
182
Notes:
Cache
Cache
Write
Read
1. Single read, single write, cache update, and writethrough = 1 to 8 bytes. Line fill = 32-byte burst read.
2. If CACHE# is driven Low and KEN# is sampled asserted.
3. If PWT is driven Low and WB/WT# is sampled High, the line is cached in the exclusive (writeback) state.
4. A write cycle occurs only if the write allocate conditions as specified in “Write Allocate” on page 177 are not met.
–
Not applicable or none.
®
Type
Processor Data Sheet
Write Miss
Read Miss
Write Hit
Read
Hit
Cache States
exclusive or modified
Cache State Before
bus, the two cache-line fills typically appear as two 32-byte
burst read cycles occurring back-to-back or, if allowed, as
p i p e l in e d cy c le s . The b u rst re a d cy c l e s d o n o t o c c u r
back-to-back (wait states occur) if the processor is not ready to
start a new cycle, if higher priority data read or write requests
exist, or if NA# (next address) was sampled negated. Wait states
can also exist between burst cycles if the processor samples
AHOLD or BOFF# asserted.
Table 30 shows all the possible cache-line states before and
after program-generated accesses to individual cache lines. The
table includes the correspondence between MESI states and
writethrough or writeback states for lines in the data cache.
exclusive
modified
Access
shared
shared
invalid
invalid
invalid
Preliminary Information
Cache Organization
cache update and
cache update
single write
(cacheable)
burst read
single write
single read
Access
Type
–
–
–
1
2
4
MESI State
exclusive
exclusive
shared or
shared or
exclusive
modified
modified
invalid
shared
invalid
Cache State After Access
3
3
Writethrough State
20695H/0—March 1998
writethrough or
writethrough or
writethrough
Writeback
writeback
writeback
writeback
writeback
writeback
–
–
Chapter 8
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