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Volume 4: Base IA-32 Instruction Reference
CPUID—CPU Identification
(Continued)
When the input value in EAX is 1, three unrelated pieces of information are returned to
the EBX register:
• Brand index (low byte of EBX)
–
this number provides an entry into a brand string
table that contains brand strings for IA-32 processors. Please refer to AP-485,
Intel
®
Processor Identification and the CPUID Instruction
(Order Number 241618)
for information on brand indices.
Note:
The Brand index field is not supported for processors based on Itanium
architecture, zero (unsupported encoding) is returned.
• CLFLUSH instruction cache line size (second byte of EBX)
–
this number indicates
the size of the cache line flushed with CLFLUSH instruction in 8-byte increments.
This field is valid only when the CLFSH feature flag is set.
• Local APIC ID (high byte of EBX)
–
this number is the 8-bit ID that is assigned to
the local APIC on the processor during power up.
Note:
The local APIC ID field is invalid for processors based on the Itanium
architecture, reserved value is returned. Software should check the
feature flags to make sure they are not running on processors based on
the Itanium architecture before interpreting the return value in this
field.
When the EAX register contains a value of 1, the CPUID instruction (in addition to
loading the processor signature in the EAX register) loads the EDX register with the
feature flags. The feature flags (when a Flag = 1) indicate what features the processor
supports.
lists the currently defined feature flag values.
A feature flag set to 1 indicates the corresponding feature is supported. Software
should identify Intel as the vendor to properly interpret the feature flags.
Table 2-5.
Feature Flags Returned in EDX Register
Bit
Mnemonic
Description
0
FPU
Floating Point Unit On-Chip.
The processor contains an x87 FPU.
1
VME
Virtual 8086 Mode Enhancements.
Virtual 8086 mode
enhancements, including CR4.VME for controlling the feature,
CR4.PVI for protected mode virtual interrupts, software interrupt
indirection, expansion of the TSS with the software indirection bitmap,
and EFLAGS.VIF and EFLAGS.VIP flags.
2
DE
Debugging Extensions.
Support for I/O breakpoints, including
CR4.DE for controlling the feature, and optional trapping of accesses
to DR4 and DR5.
3
PSE
Page Size Extension.
Large pages of size 4Mbyte are supported,
including CR4.PSE for controlling the feature, the defined dirty bit in
PDE (Page Directory Entries), optional reserved bit trapping in CR3,
PDEs, and PTEs.
4
TSC
Time Stamp Counter.
The RDTSC instruction is supported, including
CR4.TSD for controlling privilege.
5
MSR
Model Specific Registers RDMSR and WRMSR Instructions.
The
RDMSR and WRMSR instructions are supported. Some of the MSRs
are implementation dependent.
Summary of Contents for ITANIUM ARCHITECTURE
Page 1: ......
Page 7: ...402 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 199: ...4 192 Volume 4 Base IA 32 Instruction Reference FWAIT Wait See entry for WAIT ...
Page 352: ...Volume 4 Base IA 32 Instruction Reference 4 345 ROL ROR Rotate See entry for RCL RCR ROL ROR ...
Page 589: ...4 582 Volume 4 IA 32 SSE Instruction Reference ...
Page 590: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index ...
Page 591: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 603: ...INDEX Index 12 Index for Volumes 1 2 3 and 4 ...
Page 604: ......