Intel 64 and IA-32 Architectures Software Developers Manual Volume 2A, Instruction Set Reference, A-M

Vol. 2 3-179
INSTRUCTION SET REFERENCE, A-M
Example 3-1. Example of Cache and TLB Interpretation
The first member of the family of Pentium 4 processors returns the following informa-
tion about caches and TLBs when the CPUID executes with an input value of 2:
EAX 66 5B 50 01H
EBX 0H
ECX 0H
EDX 00 7A 70 00H
Which means:
• The least-significant byte (byte 0) of register EAX is set to 01H. This indicates
that CPUID needs to be executed once with an input value of 2 to retrieve
complete information about caches and TLBs.
• The most-significant bit of all four registers (EAX, EBX, ECX, and EDX) is set to 0,
indicating that each register contains valid 1-byte descriptors.
• Bytes 1, 2, and 3 of register EAX indicate that the processor has:
— 50H - a 64-entry instruction TLB, for mapping 4-KByte and 2-MByte or 4-
MByte pages.
— 5BH - a 64-entry data TLB, for mapping 4-KByte and 4-MByte pages.
— 66H - an 8-KByte 1st level data cache, 4-way set associative, with a 64-Byte
cache line size.
• The descriptors in registers EBX and ECX are valid, but contain NULL descriptors.
• Bytes 0, 1, 2, and 3 of register EDX indicate that the processor has:
— 00H - NULL descriptor.
— 70H - Trace cache: 12 K
-μop, 8-way set associative.
— 7AH - a 256-KByte 2nd level cache, 8-way set associative, with a sectored,
64-byte cache line size.
— 00H - NULL descriptor.
B0H Instruction TLB: 4 KByte pages, 4-way set associative, 128 entries
B3H Data TLB: 4 KByte pages, 4-way set associative, 128 entries
B4H Data TLB1: 4 KByte pages, 4-way associative, 256 entries
F0H 64-Byte prefetching
F1H 128-Byte prefetching
Table 3-17. Encoding of Cache and TLB Descriptors (Contd.)
Descriptor Value Cache or TLB Description