Debug store a value of 1 indicates the processor

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Unformatted text preview: 6 mode enhancements, including CR4.VME for controlling the feature, CR4.PVI for protected mode virtual interrupts, software interrupt indirection, expansion of the TSS with the software indirection bitmap, and EFLAGS.VIF and EFLAGS.VIP flags. Vol. 2 3-173 INSTRUCTION SET REFERENCE, A-M Table 3-16. More on Feature Information Returned in the EDX Register (Contd.) Bit # 2 3 Mnemonic DE PSE Description Debugging Extensions. Support for I/O breakpoints, including CR4.DE for controlling the feature, and optional trapping of accesses to DR4 and DR5. Page Size Extension. Large pages of size 4 MByte are supported, including CR4.PSE for controlling the feature, the defined dirty bit in PDE (Page Directory Entries), optional reserved bit trapping in CR3, PDEs, and PTEs. Time Stamp Counter. The RDTSC instruction is supported, including CR4.TSD for controlling privilege. Model Specific Registers RDMSR and WRMSR Instructions. The RDMSR and WRMSR instructions are supported. Some of the MSRs are implementation dependent. Physical Address Extension. Physical addresses greater than 32 bits are supported: extended page table entry formats, an extra level in the page translation tables is defined, 2-MByte pages are supported instead of 4 Mbyte pages if PAE bit is 1. The actual number of address bits beyond 32 is not defined, and is implementation specific. Machine Check Exception. Exception 18 is defined for Machine Checks, including CR4.MCE for controlling the feature. This feature does not define the model-specific implementations of machine-check error logging, reporting, and processor shutdowns. Machine Check exception handlers may have to depend on processor version to do model specific processing of the exception, or test for the presence of the Machine Check feature. CMPXCHG8B Instruction. The compare-and-exchange 8 bytes (64 bits) instruction is supported (implicitly locked and atomic). APIC On-Chip. The processor contains an Advanced Programmable Interrupt Controller (APIC), responding to memory mapped commands in the physical address range FFFE0000H to FFFE0FFFH (by default - some processors permit the APIC to be relocated). Reserved SYSENTER and SYSEXIT Instructions. The SYSENTER and SYSEXIT and associated MSRs are supported. Memory Type Range Registers. MTRRs are supported. The MTRRcap MSR contains feature bits that describe what memory types are supported, how many variable MTRRs are supported, and whether fixed MTRRs are supported. PTE Global Bit. The global bit in page directory entries (PDEs) and page table entries (PTEs) is supported, indicating TLB entries that are common to different processes and need not be flushed. The CR4.PGE bit controls this feature. 4 5 TSC MSR 6 PAE 7 MCE 8 9 CX8 APIC 10 11 12 Reserved SEP MTRR 13 PGE 3-174 Vol. 2 INSTRUCTION SET REFERENCE, A-M Table 3-16. More on Feature Information Returned in the EDX Register (Contd.) Bit # 14 Mnemonic MCA Description Machine Check Architecture. The Machine Check Architecture, which provides...
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