GX1 Datasheet, PDF (220/247 Pages) National Semiconductor (TI) – Processor Series Low Power Integrated x86 Solution

Instruction Set (Continued)
8.2.2 Extended CPUID Levels
Testing for extended CPUID instruction support can be
accomplished by executing a CPUID instruction with the
EAX register initialized to 80000000h. If a value greater
than or equal to 80000000h is returned to the EAX regis-
ter by the CPUID instruction, the processor supports
extended CPUID levels.
8.2.2.1 CPUID Instruction with EAX = 8000 0000h
Extended function 80000000h (EAX = 80000000h) of the
CPUID instruction returns the maximum extended CPUID
levels supported by the current processor in EAX (Table 8-
21). The EBX, ECX, and EDX registers are currently
reserved.
Table 8-22. EAX, EBX, ECX CPUID Data
Returned when EAX = 80000001h
Register
Returned
Contents
Description
EAX[3:0]
EAX[7:4]
EAX[11:8]
EAX[15:12]
EAX[31:16]
EBX
ECX
xx
Stepping ID
4
Model
5
Family
0
Processor Type
-
Reserved
-
Reserved
-
Reserved
Table 8-21. Maximum Extended CPUID Level
Register
Returned
Contents
Description
EAX
EBX
ECX
EDX
8000 0005h
-
-
-
Maximum Extended CPUID
Level (six levels)
Reserved
Reserved
Reserved
8.2.2.2 CPUID Instruction with EAX = 80000001h
Extended function 80000001h (EAX = 80000001h) of the
CPUID instruction returns the processor type, family,
model, and stepping information of the current processor
in EAX. The EBX and ECX registers are reserved.
The extended feature flags supported are returned in the
EDX register as shown in Table 8-23. Each flag refers to a
specific feature and indicates if that feature is present on
the processor. Some of these features have protection
control in CR4. Before using any of these features on the
processor, the software should check the corresponding
feature flag.
Table 8-23. EDX CPUID Data Returned
when EAX = 80000001h
EDX
Returned
Contents¹
Feature Flag
CR4
Bit
EDX[0]
1
EDX[1]
0
EDX[2]
0
EDX[3]
0
EDX[4]
1
EDX[5]
1
EDX[6]
0
EDX[7]
0
EDX[8]
1
EDX[9]
0
EDX[10]
0
EDX[11]
0
EDX[12]
0
EDX[13]
0
EDX[14]
0
EDX[15]
1
EDX[16]
0
EDX[22:17]
0
EDX[23]
1
EDX[24]
1
1. 0 = Not supported
FPU On-Chip
-
Virtual Mode Extension
-
Debugging Extension
-
Page Size Extension
-
(4 MB)
Time Stamp Counter
2
Model-Specific Registers
-
(via RDMSR / WRMSR
Instructions)
Reserved
-
Machine Check Exception -
CMPXCHG8B Instruction
-
Reserved
-
Reserved
-
SYSCALL / SYSRET
-
Instruction
Reserved
-
Page Global Enable
-
Reserved
-
Integer Conditional Move
-
Instruction
FPU Conditional Move
-
Instruction
Reserved
-
MMX
-
6x86MX Multimedia
-
Extensions
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