Intel IA-32 - Manual (Page 296)

7-28 Vol. 3A
MULTIPLE-PROCESSOR MANAGEMENT
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Debug registers (DR0, DR1, DR2, DR3, DR6, DR7) and the debug control MSRs
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Machine check global status (IA32_MCG_STATUS) and machine check capability
(IA32_MCG_CAP) MSRs
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Thermal clock modulation and ACPI Power management control MSRs
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Time stamp counter MSRs
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Most of the other MSR registers, including the page attribute table (PAT). See the
exceptions below.
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Local APIC registers.
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Additional general purpose registers (R8-R15), XMM registers (XMM8-XMM15), control
register, IA32_EFER on processors that support Intel EM64T.
The following features are shared by logical processors:
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IA32_MISC_ENABLE MSR (MSR address 1A0H)
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Memory type range registers (MTRRs)
Whether the following features are shared or duplicated is implementation-specific:
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Machine check architecture (MCA) MSRs (except for the IA32_MCG_STATUS and
IA32_MCG_CAP MSRs)
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Performance monitoring control and counter MSRs
7.8.2 APIC Functionality
When a processor supporting Hyper-Threading Technology support is initialized, each logical
processor is assigned a local APIC ID (see Table 8-1). The local APIC ID serves as an ID for
the logical processor and is stored in the logical processor’s APIC ID register. If two or more
IA-32 processors supporting Hyper-Threading Technology are present in a dual processor (DP)
or MP system, each logical processor on the system bus is assigned a unique local APIC ID (see
Section 7.10.2, “Identifying Logical Processors in an MP System”).
Software communicates with local processors using the APIC’s interprocessor interrupt (IPI)
messaging facility. Setup and programming for APICs is identical in processors that support and
do not support Intel Hyper-Threading Technology. See Chapter 8, “Advanced Programmable
Interrupt Controller (APIC),” for a detailed discussion.
7.8.3 Memory Type Range Registers (MTRR)
MTRRs in a processor supporting Hyper-Threading Technology are shared by logical proces-
sors. When one logical processor updates the setting of the MTRRs, settings are automatically
shared with the other logical processors in the same physical package.
IA-32 architecture requires that all MP systems based on IA-32 processors (this includes logical
processors) MUST use an identical MTRR memory map. This gives software a consistent view