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AMD AMD-K6-2/450 Design Guide - Page 73

Testing For Extended Functions, Determining the Processor Signature

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23913A/0-November 2000 Preliminary Information Embedded AMD-K6™ Processors BIOS Design Guide AMD's definition for subsequent CPUID functions and the registers returned for those functions. Once the software identifies the processor's vendor, it knows the definition for all the functions supplied by the CPUID instruction. By using these functions, the software obtains the processor information needed to properly tune its functionality to the capabilities of the processor. Testing For Extended Functions Software must test for extended functions with function 8000_0000h. The EAX register returns the largest extended function input value defined for the CPUID instruction on the processor. If this value is at least 8000_0001h, extended functions are supported. With one exception, the AMD extended feature flags include all the information provided in the standard feature flags as well as indicators for the additional AMD processor-specific feature enhancements. The duplication of standard feature bits within the extended feature bits can minimize the number of function calls required by software. The exception is bit 11, which indicates that the SYSENTER and SYSEXIT instructions are supported in the standard features and that the SYSCALL and SYSRET instructions are supported in the extended features. Determining the Processor Signature Standard function 1 (EAX=1) of the CPUID instruction returns the standard processor signature and feature bits. The standard processor signature is returned in the EAX register and provides information regarding the specific revision (stepping) and model of the processor and the instruction family level supported by the processor. The revision level can be used to determine if the processor supports specific features. However, it is not recommended that the revision level be used in this manner unless this information is not available through the standard or extended feature bits. Embedded AMD Processor Recognition 61

Section	Page
Contents	3
List of Figures	7
List of Tables	9
Revision History	11
Introduction	13
Audience	13
Processor Models and Steppings	14
AMDK6™E Embedded Processor	15
Model 7	15
AMDK6™2 Processor	15
Model 8/[7:0]	15
Model 8/[F:8]	15
AMDK6™2E Embedded Processor	16
Model 8/[F:8]	16
AMDK6™2E+ Embedded Processor	16
Model D/[7:4]	16
AMDK6™III Processor	17
Model 9/[3:0]	17
AMDK6™IIIE+ Embedded Processor	17
Model D/[3:0]	17
BIOS Consideration Checklist	18
CPUID	18
CPU Speed Detection	18
ModelSpecific Registers (MSRs)	18
Cache Testing	19
SMM Issues	19
States after RESET and INIT	20
Register States after RESET and INIT	20
Processor State after INIT	21
BuiltIn SelfTest (BIST)	22
CPUID Identification Algorithms	23
System Management Mode (SMM)	25
StateSave Map Differences	25
I/O Trap Dword Differences	25
ModelSpecific Registers Overview	26
Standard Model-Specific Registers (All Models)	28
MachineCheck Address Register (MCAR) and MachineCheck Type Register (MCTR)	28
Test Register 12 (TR12)	28
Time Stamp Counter (TSC)	28
Model 7 and Model 8/[7:0] Registers	29
Extended Feature Enable Register (EFER)	30
Write Handling Control Register (WHCR)	31
Write Allocation	31
Write Cacheability Detection Enable Bit	32
Write Allocate Enable Limit Field	32
Write Allocate Enable 15to16Mbyte Field.	33
SYSCALL/SYSRET Target Address Register (STAR)	34
Model 8/[F:8] Registers	35
Extended Feature Enable Register (EFER)	36
External Write Buffer Empty Control Field	36
Write Handling Control Register (WHCR)	39
Write Allocation	39
Write Allocate Enable Limit Field	40
Write Allocate Enable 15to16Mbyte Field	41
UC/WC Cacheability Control Register (UWCCR)	42
Physical Base Address n (n=0, 1)	43
Physical Address Mask n (n=0, 1)	43
WCn (n=0, 1)	43
UCn (n=0, 1)	43
Memory-Range Restrictions	44
Examples	45
Processor State Observability Register (PSOR)	46
NOL2 Bit	46
STEP Field	46
BF Field	46
Page Flush/Invalidate Register (PFIR)	48
LINPAGE Field	48
PF Bit	48
F/I Bit	49
Model 9 Registers	50
Extended Feature Enable Register (EFER)	51
Level-2 Cache Array Access Register (L2AAR)	52
LRU (Least Recently Used) Field	55
Writing to L2 Tag of AMDK6™III Processor	55
Model D Registers	57
Processor State Observability Register (PSOR) (Low-Power Versions)	58
PBF[2:0] Field	58
VID Field	58
NOL2 Bit	59
STEP Field	59
EBF[2:0] Field	59
Level-2 Cache Array Access Register (L2AAR)	60
LRU (Least Recently Used) Field	64
Writing to L2 Tag of AMDK6IIIE+ Processor	65
Enhanced Power Management Register (EPMR) (Low-Power Versions)	66
EPM 16-Byte I/O Block (Low-Power Versions Only)	67
BVC Field	67
Embedded AMD Processor Recognition	69
CPUID Instruction Overview	69
Testing for the CPUID Instruction	70
Illegal Instruction Exception Method	70
EFLAGS IDBit Method	70
Using CPUID Functions	71
Identifying the Processor’s Vendor	72
Testing For Extended Functions	73
Determining the Processor Signature	73
Identifying Supported Features	75
Determining Instruction Set Support	76
Detection Algorithm for Determining Instruction Set Support	77
CPUID Test	77
Standard Function Test	77
MMX™ Test	77
Optional SSE Test	77
Extended Functions Test	77
3DNow!™ Test	77
Vendor Check	77
3DNow! Extensions Test	78
AMD Multimedia Instruction Extensions Test	78
AMD Processor Signature (Extended Function)	78
Displaying the Processor’s Name	78
Displaying Cache Information	79
Determining AMDPowerNow!™ Technology Information	79
Sample Code	79
New AMDK6™ Processor Instructions	80
Additional Considerations	81
Software Timing Dependencies Relative to Memory Controller Setup	81
Pipelining Support	81
Read-Only Memory	82
Appendix A	83
CPUID	83
Standard Functions	84
Extended Functions	87
Cache Associativity Field Definitions	92
Associativity for L1 Caches and L1 TLBs	92
Associativity for L2 Cache	92
Appendix B	93
Values Returned by the CPUID Instruction	93