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CPUID (continued)
Extended Levels
Extended CPUID Level support testing consists of executing a CPUID instruction with the EAX register initialized to 8000 0000h and testing the return value in EAX. If a value greater than or equal to 8000 0000h is returned to the EAX register by the CPUID instruction, the processor supports extended CPUID Levels.
CPUID Instruction with EAX = 8000 0000h
Extended function 8000 0000h (EAX = 80000000h) of the CPUID instruction returns the maximum extended CPUID levels supported by the current processor in EAX. The other registers are reserved.
|
Register |
Description |
| EAX | Maximum Standard Levels |
| EBX-ECX-EDX | Reserved |
|
Description |
MediaGX
MMX Enhanced |
| Max Extended Levels | 80000005h |
CPUID Instruction with EAX = 8000 0001h
Extended function 8000 0001h (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.
|
Register |
Description |
| EAX[3:0] | Stepping ID |
| EAX[7:4] | Model |
| EAX[11:8] | Family |
| EAX[15:12] | Type |
| EAX[31:16] | Reserved |
|
Description
|
MediaGX
MMX Enhanced
|
| Stepping ID | xx |
| Model | 4 |
| Family | 5 |
| Type | 0 |
The Extended Feature Flags supported are returned in the EDX register. 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.
|
Feature Flag |
EDX Bit |
CR4 Bit |
MediaGX
MMX Enhanced |
| FPU On-chip | 0 | - | x |
| Virtual Mode Extension | 1 | 0,1 | - |
| Debugging Extension | 2 | 3 | - |
| Page Size Extension | 3 | 4 | - |
| Time Stamp Counter | 4 | 2 | x |
| Cyrix Model-Specific Registers | 5 | 8 | x |
| Undefined | 6 | - | - |
| Machine Check Exception | 7 | 6 | - |
| CMPXCHG8B Instruction | 8 | - | x |
| Undefined | 9 | - | - |
| Undefined | 10 | - | - |
| SYSCALL / SYSRET Instructions | 11 | - | - |
| Undefined | 12 | - | - |
| Page Global Enable | 13 | 7 | - |
| Undefined | 14 | - | - |
| Integer Cond. Move Instruction | 15 | - | x |
| FPU Cond. Move Instruction | 16 | - | - |
| Undefined | 17-22 | - | - |
| MMX Instructions | 23 | - | x |
| 6x86MX Multimedia Extensions | 24 | - | - |
| Undefined | 25-31 | - | - |
CPUID Instruction with EAX = 8000 0002h - 8000 0004h
Extended function 8000 0002h through 8000 0004 (EAX = 80000002h, 80000003h, 80000004h) of the CPUID instruction returns an ASCII string containing the name of the current processor. These functions eliminate the need to look up the processor name in a lookup table. Software can simply call these functions to obtain the name of the processor. The string may be 48 ASCII characters long, and is returned in little endian format. If the name is shorter than 48 characters long, the remaining bytes will be filled with ASCII NULL character (00h).
|
8000 0002h |
8000 0003h |
8000 0004h |
| EAX | CPU Name 1 | EAX | CPU Name 5 | EAX | CPU Name 9 |
| EBX | CPU Name 2 | EBX | CPU Name 6 | EBX | CPU Name 10 |
| ECX | CPU Name 3 | ECX | CPU Name 7 | ECX | CPU Name 11 |
| EDX | CPU Name 4 | EDX | CPU Name 8 | EDX | CPU Name 12 |
CPUID Instruction with EAX = 8000 0005h
Extended function 8000 0005h (EAX = 80000005h) of the CPUID instruction returns information about the TLB and L1 Cache to be looked up in a lookup table.
|
Register |
Description |
| EAX | Reserved |
| EBX | TLB Information |
| ECX | L1 Cache Information |
| EDX | Reserved |
|
Value |
Description |
| xxxx70xxh | TLB is 32 Entry, 4-way Set Associative, and has 4K Pages |
| xxxxxx01h | The CPUID instruction needs to be executed only once with an input value of 02h to retrieve complete information about the cache and TLB |
| xxxxxx80h | L1 Cache is 16K, 4-way Set Associative, and has 16 Bytes per Line |
|
Description |
MediaGX MMX Enhanced |
| EBX (TLB Info) | 00007001h |
| ECX (L1 Cache Info) | 00000080h |
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