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Power Management Entry and exit of the C-States at the thread and core level are shown in Figure 4-2. Figure 4-2. Thread and Core C-State Entry and Exit MWAIT(C1), HLT MWAIT(C1), HLT (C1E Enabled) C1 C1E C3 C6 While individual threads can request low power C-states, power saving actions only take place once the core C-state is resolved. Core C-states are automatically resolved by the processor. For thread and core C-states, a transition to and from C0 is required before entering any other C-state. Note: 1. If enabled, the core C-state will be C1E if all active cores have also resolved to a core C1 state or higher. 4.2.3 Requesting Low-Power Idle States C0 MWAIT(C6), P_LVL3 I/O Read MWAIT(C3), P_LVL2 I/O Read Table 4-3. Coordination of Thread Power States at the Core Level Processor Core C-State Thread 0 Thread 1 C0 C1 C3 C6 C0 C0 C0 C0 C0 C1 C0 C1 1 C1 1 C1 1 C3 C0 C1 1 C6 C0 C1 1 C3 C3 C3 C6 The primary software interfaces for requesting low-power idle states are through the MWAIT instruction with sub-state hints and the HLT instruction (for C1 and C1E). However, software may make C-state requests using the legacy method of I/O reads from the ACPI-defined processor clock control registers, referred to as P_LVLx. This method of requesting C-states provides legacy support for operating systems that initiate C-state transitions using I/O reads. For legacy operating systems, P_LVLx I/O reads are converted within the processor to the equivalent MWAIT C-state request. Therefore, P_LVLx reads do not directly result in I/O reads to the system. The feature, known as I/O MWAIT redirection, must be enabled in the BIOS. 36 Datasheet, Volume 1
Power Management Note: The P_LVLx I/O Monitor address needs to be set up before using the P_LVLx I/O read interface. Each P-LVLx is mapped to the supported MWAIT(Cx) instruction as follows: Table 4-4. P_LVLx to MWAIT Conversion The BIOS can write to the C-state range field of the PMG_IO_CAPTURE MSR to restrict the range of I/O addresses that are trapped and emulate MWAIT like functionality. Any P_LVLx reads outside of this range does not cause an I/O redirection to MWAIT(Cx) like request. They fall through like a normal I/O instruction. Note: When P_LVLx I/O instructions are used, MWAIT substates cannot be defined. The MWAIT substate is always zero if I/O MWAIT redirection is used. By default, P_LVLx I/O redirections enable the MWAIT 'break on EFLAGS.IF' feature that triggers a wakeup on an interrupt, even if interrupts are masked by EFLAGS.IF. 4.2.4 Core C-states The following are general rules for all core C-states, unless specified otherwise: • A core C-State is determined by the lowest numerical thread state (such that, Thread 0 requests C1E while thread1 requests C3, resulting in a core C1E state). See Table 4-3. • A core transitions to C0 state when: — an interrupt occurs. — there is an access to the monitored address if the state was entered using an MWAIT instruction. • For core C1/C1E, and core C3, an interrupt directed toward a single thread wakes only that thread. However, since both threads are no longer at the same core Cstate, the core resolves to C0. 4.2.4.1 Core C0 State P_LVLx MWAIT(Cx) Notes P_LVL2 MWAIT(C3) P_LVL3 MWAIT(C6) C6. No sub-states allowed • For core C6, an interrupt coming into either thread wakes both threads into C0 state. • Any interrupt coming into the processor package may wake any core. The normal operating state of a core where code is being executed. 4.2.4.2 Core C1/C1E State C1/C1E is a low power state entered when all threads within a core execute a HLT or MWAIT(C1/C1E) instruction. A System Management Interrupt (SMI) handler returns execution to either Normal state or the C1/C1E state. See the Intel ® 64 and IA-32 Architecture Software Developer’s Manual, Volume 3A/3B: System Programmer’s Guide for more information. While a core is in C1/C1E state, it processes bus snoops and snoops from other threads. For more information on C1E, see Section 4.2.5.2. Datasheet, Volume 1 37
Page 1 and 2: Intel ® Core i7-800 and i5-700 Des
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Page 7 and 8: 7-9 Control Sideband and TAP Signal
Page 9 and 10: Introduction 1 Introduction The Int
Page 11 and 12: Introduction 1.1 Processor Feature
Page 13 and 14: Introduction nonzero) with an Unsup
Page 15 and 16: Introduction 1.6 Terminology Term D
Page 17 and 18: Introduction 1.7 Related Documents
Page 19 and 20: Interfaces 2 Interfaces This chapte
Page 21 and 22: Interfaces 2.1.3.2 Dual-Channel Mod
Page 23 and 24: Interfaces 2.1.5 Technology Enhance
Page 25 and 26: Interfaces Figure 2-4. Packet Flow
Page 27 and 28: Interfaces 2.2.3 PCI Express* Ports
Page 29 and 30: Technologies 3 Technologies 3.1 Int
Page 31 and 32: Technologies 3.1.5 Intel ® VT-d Fe
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Page 35: Power Management — All active pro
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Page 41 and 42: Power Management 4.3 Integrated Mem
Page 43 and 44: Thermal Management 5 Thermal Manage
Page 45 and 46: Signal Description 6 Signal Descrip
Page 47 and 48: Signal Description Table 6-3. Memor
Page 49 and 50: Signal Description Table 6-5. Reset
Page 51 and 52: Signal Description 6.8 JTAG/ITP Sig
Page 53 and 54: Signal Description 6.10 Power Seque
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Page 57 and 58: Electrical Specifications 7 Electri
Page 59 and 60: Electrical Specifications Table 7-1
Page 65 and 66: Electrical Specifications 7.7 Test
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Processor Land and Signal Informati
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