AMD-K6-2ESLASH233AMZ datasheet(217/332 Pages) AMD

217 / 332 page

Chapter 8

Cache Organization

199

22529B/0—January 2000

AMD-K6™-2E Processor Data Sheet

Preliminary Information

8.10

Cache Coherency

Different methods exist to maintain coherency between the

system memory and cache memories. Inquire cycles, internal

snoops, FLUSH#, WBINVD, INVD, and line replacements all

prevent inconsistencies between memories.

Inquire Cycles

Inquire cycles are bus cycles initiated by system logic. These

inquiries ensure coherency between the caches and main

memory. In systems with multiple caching masters, system logic

maintains cache coherency by driving inquire cycles to the

processor. System logic initiates inquire cycles by asserting

AHOLD, BOFF#, or HOLD to obtain control of the address bus

and then driving EADS#, INV (optional), and an inquire

address (A[31:5]).

This type of bus cycle causes the processor to compare the tags

for both its instruction and data caches with the inquire

address.

If there is a hit to a shared or exclusive line in the data cache

or a valid line in the instruction cache, the processor asserts

HIT#.

If the compare hits a modified line in the data cache, the

processor asserts HIT# and HITM#. If HITM# is asserted, the

processor writes the modified line back to memory.

If INV was sampled asserted with EADS#, a hit invalidates

the line.

If INV was sampled negated with EADS#, a hit leaves the

line in the Shared state or transitions it from the Exclusive

or Modified to Shared state.

Table 35 on page 202 shows the effects of inquire cycles—

performed with INV equal to 0 (non-validating) and INV equal

to 1 (invalidating) snoops and invalidations.

Internal Snooping

Internal snooping is initiated by the processor (rather than

system logic) during certain cache accesses. It is used to

maintain coherency between the L1 instruction and data

caches.

The processor automatically snoops its instruction cache during

read or write misses to its data cache, and it snoops its data

AMD-K6-2E/233AMZ Datasheet(PDF) 217 Page - Advanced Micro Devices

AMD-K6-2E/233AMZ Datasheet(HTML) 217 Page - Advanced Micro Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL