Intel 253668-032US Manual De Usuario

Vol. 3   11-17

MEMORY CACHE CONTROL

Table 11-5.  Cache Operating Modes 

CD NW

Caching and Read/Write Policy

L1

L2/L3

1

0

0

Normal Cache Mode. Highest performance cache operation.
• Read hits access the cache; read misses may cause replacement.

• Write hits update the cache.

• Only writes to shared lines and write misses update system 

memory.

Yes

Yes

Yes

Yes

Yes

Yes

• Write misses cause cache line fills.

• Write hits can change shared lines to modified under control of 

the MTRRs and with associated read invalidation cycle.

• (Pentium processor only.) Write misses do not cause cache line 

fills.

Yes

Yes

Yes

Yes

• (Pentium processor only.) Write hits can change shared lines to 

exclusive under control of WB/WT#.

• Invalidation is allowed.

• External snoop traffic is supported.

Yes

Yes

Yes

Yes

Yes

0

1

Invalid setting.
Generates a general-protection exception (#GP) with an error code 

of 0.

NA

NA

1

0

No-fill Cache Mode. Memory coherency is maintained.

3

• (Pentium 4 and later processor families.) State of processor after 

a power up or reset.

• Read hits access the cache; read misses do not cause 

replacement (see Pentium 4 and Intel Xeon processors reference 

below).

• Write hits update the cache. 

• Only writes to shared lines and write misses update system 

memory.

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

• Write misses access memory.

• Write hits can change shared lines to exclusive under control of 

the MTRRs and with associated read invalidation cycle.

• (Pentium processor only.) Write hits can change shared lines to 

exclusive under control of the WB/WT#.

Yes

Yes

Yes

Yes

Yes

1

0

• (P6 and later processor families only.) Strict memory ordering is 

not enforced unless the MTRRs are disabled and/or all memory is 

referenced as uncached (see Section 7.2.4., “Strengthening or 

Weakening the Memory Ordering Model”).

• Invalidation is allowed.

• External snoop traffic is supported.

Yes

Yes

Yes

Yes

Yes

Yes