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Revision 3.1

Processor Programming (Continued)

Index E8h

CCR4 — Configuration Control Register 4 (R/W)

Default Value = 85h

7CPUID

Enable CPUID Instruction:

If = 1: The ID bit in the EFLAGS register to be modified and execution of the CPUID instruction

occurs as documented in Table 9-2 on page 202.

If = 0: The ID bit can not be modified and execution of the CPUID instruction causes an invalid

opcode exception.

6SMI_NEST

SMI Nest:

If = 1: SMI interrupts can occur during SMM mode. SMI handlers can optionally set SMI_NEST high

to allow higher-priority SMI interrupts while handling the current event

FPU_FAST_EN

FPU Fast Mode Enable:

If = 0: Disable FPU Fast Mode

If = 1: Enable FPU Fast Mode.

4DTE_EN

Directory Table Entry Cache:

If = 1: Enables directory table entry to be cached.

Cleared to 0 at reset.

3MEM_BYP

Memory Read Bypassing:

If = 1: Enables memory read bypassing.

Cleared to 0 at reset.

2:0

IORT(2:0)

I/O Recovery Time: Specifies the minimum number of bus clocks between I/O accesses:

000 = No clock delay

100 = 16-clock delay

001 = 2-clock delay

101 = 32-clock delay (default value after reset)

010 = 4-clock delay

110 = 64-clock delay

011 = 8-clock delay

111 = 128-clock delay

Cleared to 0 at reset.

Note: MAPEN (CCR3[4]) must = 1 to read or write to this register.

Index EBh

CCR7 — Configuration Control Register 7 (R/W)

Default Value = 00h

7:3

RSVD

Reserved: Set to 0.

2NMI

Generate NMI:

0 = Do nothing

1 = Generate NMI

In order to generate multiple NMIs, this bit must be set to zero between each setting of 1.

1RSVD

Reserved: Set to 0.

0EMMX

Extended MMX Instructions Enable:

If = 1: extended MMX instructions are enabled

Index 20h

PCR — Performance Control Register (R/W)

Default Value = 07h

LSSER

Load/Store Serialize Enable (Reorder Disable): LSSER should be set to ensure that memory-

mapped I/O devices operating outside of the address range 640K to 1M will operate correctly. For

memory accesses above 1 GB, refer to CCR3[7:5] (LSS_34, LSS_23, LSS_12.)

If = 1: All memory read and write operations will occur in execution order (load/store serializing

enabled, reordering disabled).

If = 0: Memory reads and write can be reordered for optimum performance (load/store serializing

disabled, reordering enabled).

Memory accesses in the address range 640K to 1M will always be issued in execution order.

6RSVD

Reserved: Set to 0.

5RSVD

Reserved: This is a test bit that must be set to 0.

4:0

RSVD

Reserved: Set to 0.

Note: MAPEN (CCR3[4]) must = 1 to read or write to this register.

Index B0h, B1h, B2h, B3h

SMHR — SMI Header Address Register (R/W)

Default Value = xxh

Table 3-11. Configuration Registers (Continued)

Bit

Name

Description

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