Intel 64 and IA-32 Architectures Software Developers Manual Volume 2B, Instruction Set Reference, N-Z
Vol. 2B 4-143
INSTRUCTION SET REFERENCE, N-Z
PREFETCHh—Prefetch Data Into Caches
Description
Fetches the line of data from memory that contains the byte specified with the source
operand to a location in the cache hierarchy specified by a locality hint:
• T0 (temporal data)—prefetch data into all levels of the cache hierarchy.
—Pentium III processor—1st- or 2nd-level cache.
— Pentium 4 and Intel Xeon processors—2nd-level cache.
• T1 (temporal data with respect to first level cache)—prefetch data into level 2
cache and higher.
—Pentium III processor—2nd-level cache.
— Pentium 4 and Intel Xeon processors—2nd-level cache.
• T2 (temporal data with respect to second level cache)—prefetch data into level 2
cache and higher.
—Pentium III processor—2nd-level cache.
— Pentium 4 and Intel Xeon processors—2nd-level cache.
• NTA (non-temporal data with respect to all cache levels)—prefetch data into non-
temporal cache structure and into a location close to the processor, minimizing
cache pollution.
—Pentium III processor—1st-level cache
— Pentium 4 and Intel Xeon processors—2nd-level cache
The source operand is a byte memory location. (The locality hints are encoded into
the machine level instruction using bits 3 through 5 of the ModR/M byte. Use of any
ModR/M value other than the specified ones will lead to unpredictable behavior.)
If the line selected is already present in the cache hierarchy at a level closer to the
processor, no data movement occurs. Prefetches from uncacheable or WC memory
are ignored.
Opcode Instruction
64-Bit
Mode
Compat/
Leg Mode Description
0F 18
/1
PREFETCHT0 m8 Valid Valid Move data from m8 closer to the
processor using T0 hint.
0F 18
/2
PREFETCHT1 m8 Valid Valid Move data from m8 closer to the
processor using T1 hint.
0F 18
/3
PREFETCHT2 m8 Valid Valid Move data from m8 closer to the
processor using T2 hint.
0F 18
/0
PREFETCHNTA m8 Valid Valid Move data from m8 closer to the
processor using NTA hint.