1.\" 2.\" Copyright (c) 2001 Michael Smith 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.\" $FreeBSD: src/share/man/man4/acpi.4,v 1.61.8.1 2009/04/15 03:14:26 kensmith Exp $ 27.\" 28.Dd June 21, 2015 29.Dt ACPI 4 30.Os 31.Sh NAME 32.Nm acpi 33.Nd Advanced Configuration and Power Management support 34.Sh SYNOPSIS 35.Cd "device acpi" 36.Pp 37.Cd "options ACPI_DEBUG" 38.Cd "options DDB" 39.Sh DESCRIPTION 40The 41.Nm 42driver provides support for the Intel/Microsoft/Compaq/Toshiba ACPI 43standard. 44This support includes platform hardware discovery (superseding the 45PnP and PCI BIOS), as well as power management (superseding APM) and 46other features. 47ACPI core support is provided by the ACPICA reference implementation 48from Intel. 49.Pp 50Note that the 51.Nm 52driver is automatically loaded by the 53.Xr loader 8 , 54and should only be 55compiled into the kernel on platforms where ACPI is mandatory. 56.Sh SYSCTL VARIABLES 57The 58.Nm 59driver is intended to provide power management without user intervention. 60If the default settings are not optimal, the following sysctls can be 61used to modify or monitor 62.Nm 63behavior. 64.Bl -tag -width indent 65.It Va debug.acpi.enable_debug_objects 66Enable dumping Debug objects without 67.Cd "options ACPI_DEBUG" . 68Default is 0, ignore Debug objects. 69.It Va hw.acpi.acline 70AC line state (1 means online, 0 means on battery power). 71.It Va hw.acpi.cpu.cx_usage 72Debugging information listing the percent of total usage for each sleep state. 73The values are reset when 74.Va hw.acpi.cpu.cx_lowest 75is modified. 76.It Va hw.acpi.cpu.cx_lowest 77Lowest Cx state to use for idling the CPU. 78A scheduling algorithm will select states between 79.Li C1 80and this setting 81as system load dictates. 82To enable ACPI CPU idling control, 83.Va machdep.cpu_idle_hlt 84must be set to 2 (the default value). 85.It Va hw.acpi.cpu.cx_supported 86List of supported CPU idle states and their transition latency 87in microseconds. 88Each state has a type (e.g., 89.Li C2 ) . 90.Li C1 91is equivalent to the ia32 92.Li HLT 93instruction, 94.Li C2 95provides a deeper 96sleep with the same semantics, and 97.Li C3 98provides the deepest sleep 99but additionally requires bus mastering to be disabled. 100States greater than 101.Li C3 102provide even more power savings with the same 103semantics as the 104.Li C3 105state. 106Deeper sleeps provide more power savings but increased transition 107latency when an interrupt occurs. 108.It Va hw.acpi.disable_on_reboot 109Disable ACPI during the reboot process. 110Most systems reboot fine with ACPI still enabled, but some require 111exiting to legacy mode first. 112Default is 0, leave ACPI enabled. 113.It Va hw.acpi.handle_reboot 114Use the ACPI Reset Register capability to reboot the system. 115Default is 0, use legacy reboot support. 116Some newer systems require use of this register, while some only work 117with legacy rebooting support. 118.It Va hw.acpi.lid_switch_state 119Suspend state 120.Pq Li S1 Ns \[en] Ns Li S5 121to enter when the lid switch (i.e., a notebook screen) is closed. 122Default is 123.Dq Li NONE 124(do nothing). 125.It Va hw.acpi.power_button_state 126Suspend state 127.Pq Li S1 Ns \[en] Ns Li S5 128to enter when the power button is pressed. 129Default is 130.Li S5 131(power-off nicely). 132.It Va hw.acpi.install_interface , hw.acpi.remove_interface 133Install or remove OS interface(s) to control the return value of the 134.Ql _OSI 135query method. 136When an OS interface is specified in 137.Va hw.acpi.install_interface , 138the 139.Li _OSI 140query for the interface returns it is 141.Em supported . 142Conversely, when an OS interface is specified in 143.Va hw.acpi.remove_interface , 144the 145.Li _OSI 146query returns it is 147.Em not supported . 148Multiple interfaces can be specified in a comma-separated list and 149any leading white spaces will be ignored. 150For example, 151.Qq Li FreeBSD, Linux 152is a valid list of two interfaces 153.Qq Li FreeBSD 154and 155.Qq Li Linux . 156.It Va hw.acpi.reset_video 157Reset the video adapter from real mode during the resume path. 158Some systems need this help, others have display problems if it is enabled. 159Default is 0 (disabled). 160.It Va hw.acpi.s4bios 161Indicate whether the system supports 162.Li S4BIOS . 163This means that the BIOS can handle all the functions of suspending the 164system to disk. 165Otherwise, the OS is responsible for suspending to disk 166.Pq Li S4OS . 167Most current systems do not support 168.Li S4BIOS . 169.It Va hw.acpi.sleep_button_state 170Suspend state 171.Pq Li S1 Ns \[en] Ns Li S5 172to enter when the sleep button is pressed. 173This is usually a special function button on the keyboard. 174Default is 175.Li S3 176(suspend-to-RAM). 177.It Va hw.acpi.sleep_delay 178Wait this number of seconds between preparing the system to suspend and 179actually entering the suspend state. 180Default is 1 second. 181.It Va hw.acpi.supported_sleep_state 182Suspend states 183.Pq Li S1 Ns \[en] Ns Li S5 184supported by the BIOS. 185.Bl -tag -width indent 186.It Li S1 187Quick suspend to RAM. 188The CPU enters a lower power state, but most peripherals are left running. 189.It Li S2 190Lower power state than 191.Li S1 , 192but with the same basic characteristics. 193Not supported by many systems. 194.It Li S3 195Suspend to RAM. 196Most devices are powered off, and the system stops running except for 197memory refresh. 198.It Li S4 199Suspend to disk. 200All devices are powered off, and the system stops running. 201When resuming, the system starts as if from a cold power on. 202Not yet supported by 203.Fx 204unless 205.Li S4BIOS 206is available. 207.It Li S5 208System shuts down cleanly and powers off. 209.El 210.It Va hw.acpi.verbose 211Enable verbose printing from the various ACPI subsystems. 212.El 213.Sh LOADER TUNABLES 214Tunables can be set at the 215.Xr loader 8 216prompt before booting the kernel or stored in 217.Pa /boot/loader.conf . 218Many of these tunables also have a matching 219.Xr sysctl 8 220entry for access after boot. 221.Bl -tag -width indent 222.It Va acpi_dsdt_load 223Enables loading of a custom ACPI DSDT. 224.It Va acpi_dsdt_name 225Name of the DSDT table to load, if loading is enabled. 226It is relative to 227.Pa /boot/kernel . 228.It Va debug.acpi.disabled 229Selectively disables portions of ACPI that are enabled by default, for 230debugging purposes. 231.It Va debug.acpi.enabled 232Selectively enables portions of ACPI that are disabled by default, for 233debugging purposes. 234.It Va debug.acpi.facs_addr32 235Favor 32-bit FACS table addresses over the 64-bit addresses. 236.It Va debug.acpi.fadt_addr32 237Favor 32-bit FADT register addresses over the 64-bit addresses. 238.It Va debug.acpi.ignore_xsdt 239Ignore the XSDT, forcing the use of the RSDT. 240.It Va debug.acpi.interpreter_slack 241Enable less strict ACPI implementations. 242Default is 1, ignore common BIOS mistakes. 243.It Va debug.acpi.max_threads 244Specify the number of task threads that are started on boot. 245Limiting this to 1 may help work around various BIOSes that cannot 246handle parallel requests. 247The default value is 3. 248.It Va debug.acpi.quirks 249Override any automatic quirks completely. 250.It Va debug.acpi.resume_beep 251Beep the PC speaker on resume. 252This can help diagnose suspend/resume problems. 253Default is 0 (disabled). 254.It Va hint.acpi.0.disabled 255Set this to 1 to disable all of ACPI. 256If ACPI has been disabled on your system due to a blacklist entry for your 257BIOS, you can set this to 0 to re-enable ACPI for testing. 258.It Va hw.acpi.ec.poll_timeout 259Delay in milliseconds to wait for the EC to respond. 260Try increasing this number if you get the error 261.Qq Li AE_NO_HARDWARE_RESPONSE . 262.It Va hw.acpi.host_mem_start 263Override the assumed memory starting address for PCI host bridges. 264.It Va hw.acpi.reset_video 265Enables calling the VESA reset BIOS vector on the resume path. 266This can fix some graphics cards that have problems such as LCD white-out 267after resume. 268Default is 0 (disabled). 269.It Va hw.acpi.auto_serialize_methods 270Auto-serialization of control methods to proactively prevent problems with 271ill-behaved reentrant control methods that create named ACPI objects. 272Default is 1 (enabled). 273.It Va hw.acpi.verbose 274Turn on verbose debugging information about what ACPI is doing. 275.It Va hw.pci.link.%s.%d.irq 276Override the interrupt to use for this link and index. 277This capability should be used carefully, and only if a device is not 278working with 279.Nm 280enabled. 281.Qq %s 282is the name of the link (e.g., LNKA). 283.Qq %d 284is the resource index when the link supports multiple IRQs. 285Most PCI links only have one IRQ resource, so the below form should be used. 286.It Va hw.pci.link.%s.irq 287Override the interrupt to use. 288This capability should be used carefully, and only if a device is not 289working with 290.Nm 291enabled. 292.Qq %s 293is the name of the link (e.g., LNKA). 294.El 295.Sh DISABLING ACPI 296Since ACPI support on different platforms varies greatly, there are many 297debugging and tuning options available. 298.Pp 299For machines known not to work with 300.Nm 301enabled, there is a BIOS blacklist. 302Currently, the blacklist only controls whether 303.Nm 304should be disabled or not. 305In the future, it will have more granularity to control features (the 306infrastructure for that is already there). 307.Pp 308To enable 309.Nm 310(for debugging purposes, etc.) on machines that are on the blacklist, set the 311kernel environment variable 312.Va hint.acpi.0.disabled 313to 0. 314Before trying this, consider updating your BIOS to a more recent version that 315may be compatible with ACPI. 316.Pp 317To disable the 318.Nm 319driver completely, set the kernel environment variable 320.Va hint.acpi.0.disabled 321to 1. 322.Pp 323Some i386 machines totally fail to operate with some or all of ACPI disabled. 324Other i386 machines fail with ACPI enabled. 325Disabling all or part of ACPI on non-i386 platforms (i.e., platforms where 326ACPI support is mandatory) may result in a non-functional system. 327.Pp 328The 329.Nm 330driver comprises a set of drivers, which may be selectively disabled 331in case of problems. 332To disable a sub-driver, list it in the kernel 333environment variable 334.Va debug.acpi.disabled . 335Multiple entries can be listed, separated by a space. 336.Pp 337ACPI sub-devices and features that can be disabled: 338.Bl -tag -width ".Li sysresource" 339.It Li all 340Disable all ACPI features and devices. 341.It Li acad 342.Pq Vt device 343Supports AC adapter. 344.It Li bus 345.Pq Vt feature 346Probes and attaches subdevices. 347Disabling will avoid scanning the ACPI namespace entirely. 348.It Li children 349.Pq Vt feature 350Attaches standard ACPI sub-drivers and devices enumerated in the 351ACPI namespace. 352Disabling this has a similar effect to disabling 353.Dq Li bus , 354except that the 355ACPI namespace will still be scanned. 356.It Li button 357.Pq Vt device 358Supports ACPI button devices (typically power and sleep buttons). 359.It Li cmbat 360.Pq Vt device 361Control-method batteries device. 362.It Li cpu 363.Pq Vt device 364Supports CPU power-saving and speed-setting functions. 365.It Li cpu_cst 366.Pq Vt device 367Supports CPU power-saving. 368Disabling 369.Dq Li cpu 370will also disable this device. 371.It Li cpu_pst 372.Pq Vt device 373Supports CPU speed-setting. 374Disabling 375.Dq Li cpu 376will also disable this device. 377.It Li dock 378.Pq Vt device 379Docking station device. 380.It Li ec 381.Pq Vt device 382Supports the ACPI Embedded Controller interface, used to communicate 383with embedded platform controllers. 384.It Li hpet 385.Pq Vt feature 386Supports the High Precision Event Timer. 387.It Li isa 388.Pq Vt device 389Supports an ISA bus bridge defined in the ACPI namespace, 390typically as a child of a PCI bus. 391.It Li lid 392.Pq Vt device 393Supports an ACPI laptop lid switch, which typically puts a 394system to sleep. 395.It Li quirks 396.Pq Vt feature 397Do not honor quirks. 398Quirks automatically disable ACPI functionality based on the XSDT table's 399OEM vendor name and revision date. 400.It Li pci 401.Pq Vt device 402Supports Host to PCI bridges. 403.It Li pci_link 404.Pq Vt feature 405Performs PCI interrupt routing. 406.It Li sysresource 407.Pq Vt device 408Pseudo-devices containing resources which ACPI claims. 409.It Li thermal 410.Pq Vt device 411Supports system cooling and heat management. 412.It Li timer 413.Pq Vt device 414Implements a timecounter using the ACPI fixed-frequency timer. 415.It Li video 416.Pq Vt device 417Supports 418.Xr acpi_video 4 419which may conflict with 420.Xr agp 4 421device. 422.El 423.Pp 424.\"The 425.\".Nm 426.\"driver comprises a set of drivers, 427.\"which may be selectively enabled in case of testing. 428.\"To enable a sub-driver, 429.\"list it in the kernel environment variable 430.\".Va debug.acpi.enabled . 431.\"Multiple entries can be listed, 432.\"separated by a space. 433.\".Pp 434.\"ACPI sub-devices and features that can be enabled: 435.\".Bl -tag -width ".Li sysresource" 436.\"[...] 437.\".El 438.\".Pp 439It is also possible to avoid portions of the ACPI namespace which 440may be causing problems, by listing the full path of the root of 441the region to be avoided in the kernel environment variable 442.Va debug.acpi.avoid . 443The object and all of its children will be ignored during the 444bus/children scan of the namespace. 445The ACPICA code will still know about the avoided region. 446.Sh DEBUGGING OUTPUT 447To enable debugging output, 448.Nm 449must be compiled with 450.Cd "options ACPI_DEBUG" . 451Debugging output is separated between layers and levels, where a layer is 452a component of the ACPI subsystem, and a level is a particular kind 453of debugging output. 454.Pp 455Both layers and levels are specified as a whitespace-separated list of 456tokens, with layers listed in 457.Va debug.acpi.layer 458and levels in 459.Va debug.acpi.level . 460.Pp 461The first set of layers is for ACPICA components, and the second is for 462.Dx 463drivers. 464The ACPICA layer descriptions include the prefix for the files they 465refer to. 466The supported layers are: 467.Pp 468.Bl -tag -compact -width ".Li ACPI_CA_DISASSEMBLER" 469.It Li ACPI_UTILITIES 470Utility ("ut") functions 471.It Li ACPI_HARDWARE 472Hardware access ("hw") 473.It Li ACPI_EVENTS 474Event and GPE ("ev") 475.It Li ACPI_TABLES 476Table access ("tb") 477.It Li ACPI_NAMESPACE 478Namespace evaluation ("ns") 479.It Li ACPI_PARSER 480AML parser ("ps") 481.It Li ACPI_DISPATCHER 482Internal representation of interpreter state ("ds") 483.It Li ACPI_EXECUTER 484Execute AML methods ("ex") 485.It Li ACPI_RESOURCES 486Resource parsing ("rs") 487.It Li ACPI_CA_DEBUGGER 488Debugger implementation ("db", "dm") 489.It Li ACPI_OS_SERVICES 490Usermode support routines ("os") 491.It Li ACPI_CA_DISASSEMBLER 492Disassembler implementation (unused) 493.It Li ACPI_ALL_COMPONENTS 494All the above ACPICA components 495.It Li ACPI_AC_ADAPTER 496AC adapter driver 497.It Li ACPI_BATTERY 498Control-method battery driver 499.It Li ACPI_BUS 500ACPI, ISA, and PCI bus drivers 501.It Li ACPI_BUTTON 502Power and sleep button driver 503.It Li ACPI_EC 504Embedded controller driver 505.It Li ACPI_FAN 506Fan driver 507.It Li ACPI_OEM 508Platform-specific driver for hotkeys, LED, etc. 509.It Li ACPI_POWER 510Power resource driver 511.It Li ACPI_PROCESSOR 512CPU driver 513.It Li ACPI_THERMAL 514Thermal zone driver 515.It Li ACPI_TIMER 516Timer driver 517.It Li ACPI_ALL_DRIVERS 518All the above 519.Dx 520ACPI drivers 521.El 522.Pp 523The supported levels are: 524.Pp 525.Bl -tag -compact -width ".Li ACPI_LV_AML_DISASSEMBLE" 526.It Li ACPI_LV_INIT 527Initialization progress 528.It Li ACPI_LV_DEBUG_OBJECT 529Stores to objects 530.It Li ACPI_LV_INFO 531General information and progress 532.It Li ACPI_LV_REPAIR 533Repair a common problem with predefined methods 534.It Li ACPI_LV_ALL_EXCEPTIONS 535All the previous levels 536.It Li ACPI_LV_PARSE 537.It Li ACPI_LV_DISPATCH 538.It Li ACPI_LV_EXEC 539.It Li ACPI_LV_NAMES 540.It Li ACPI_LV_OPREGION 541.It Li ACPI_LV_BFIELD 542.It Li ACPI_LV_TABLES 543.It Li ACPI_LV_VALUES 544.It Li ACPI_LV_OBJECTS 545.It Li ACPI_LV_RESOURCES 546.It Li ACPI_LV_USER_REQUESTS 547.It Li ACPI_LV_PACKAGE 548.It Li ACPI_LV_VERBOSITY1 549All the previous levels 550.It Li ACPI_LV_ALLOCATIONS 551.It Li ACPI_LV_FUNCTIONS 552.It Li ACPI_LV_OPTIMIZATIONS 553.It Li ACPI_LV_VERBOSITY2 554All the previous levels 555.It Li ACPI_LV_ALL 556Alias for 557.Qq Li ACPI_LV_VERBOSITY2 558.It Li ACPI_LV_MUTEX 559.It Li ACPI_LV_THREADS 560.It Li ACPI_LV_IO 561.It Li ACPI_LV_INTERRUPTS 562.It Li ACPI_LV_VERBOSITY3 563All the previous levels 564.It Li ACPI_LV_AML_DISASSEMBLE 565.It Li ACPI_LV_VERBOSE_INFO 566.It Li ACPI_LV_FULL_TABLES 567.It Li ACPI_LV_EVENTS 568.It Li ACPI_LV_VERBOSE 569All levels after 570.Qq Li ACPI_LV_VERBOSITY3 571.It Li ACPI_LV_INIT_NAMES 572Needs to be specified separately 573.It Li ACPI_LV_LOAD 574Needs to be specified separately 575.El 576.Pp 577Selection of the appropriate layer and level values is important 578to avoid massive amounts of debugging output. 579For example, the following configuration is a good way to gather initial 580information. 581It enables debug output for both ACPICA and the 582.Nm 583driver, printing basic information about errors, warnings, and progress. 584.Bd -literal -offset indent 585debug.acpi.layer="ACPI_ALL_COMPONENTS ACPI_ALL_DRIVERS" 586debug.acpi.level="ACPI_LV_ALL_EXCEPTIONS" 587.Ed 588.Pp 589Debugging output by the ACPICA subsystem is prefixed with the 590module name in lowercase, followed by a source line number. 591Output from the 592.Dx Ns -local 593code follows the same format, but 594the module name is uppercased. 595.Sh OVERRIDING YOUR BIOS BYTECODE 596ACPI interprets bytecode named AML 597(ACPI Machine Language) 598provided by the BIOS vendor as a memory image at boot time. 599Sometimes, the AML code contains a bug that does not appear when parsed 600by the Microsoft implementation. 601.Dx 602provides a way to override it with your own AML code to work around 603or debug such problems. 604Note that all AML in your DSDT and any SSDT tables is overridden. 605.Pp 606In order to load your AML code, copy it to 607.Pa /boot/kernel/acpi_dsdt.aml 608and add the following line to 609.Pa /boot/loader.conf . 610.Bd -literal -offset indent 611acpi_dsdt_load="YES" 612.Ed 613.Pp 614In order to prepare your AML code, you will need the 615.Xr acpidump 8 616and 617.Xr iasl 8 618utilities and some ACPI knowledge. 619.\".Sh COMPATIBILITY 620.\"ACPI is only found and supported on i386 and x86_64. 621.Sh SEE ALSO 622.Xr kenv 1 , 623.Xr acpi_asus 4 , 624.Xr acpi_dock 4 , 625.Xr acpi_fujitsu 4 , 626.Xr acpi_hp 4 , 627.Xr acpi_panasonic 4 , 628.Xr acpi_sony 4 , 629.Xr acpi_thermal 4 , 630.Xr acpi_thinkpad 4 , 631.Xr acpi_toshiba 4 , 632.Xr acpi_video 4 , 633.Xr aibs 4 , 634.Xr loader.conf 5 , 635.Xr acpibin 8 , 636.Xr acpiconf 8 , 637.Xr acpidump 8 , 638.Xr acpiexec 8 , 639.Xr acpinames 8 , 640.Xr acpixtract 8 , 641.Xr config 8 , 642.Xr iasl 8 643.Rs 644.%A "Hewlett-Packard Corporation" 645.%A "Intel Corporation" 646.%A "Microsoft Corporation" 647.%A "Phoenix Technologies Ltd." 648.%A "Toshiba Corporation" 649.%D November 13, 2013 650.%T "Advanced Configuration and Power Interface Specification" 651.%O http://acpi.info/spec.htm 652.Re 653.Sh AUTHORS 654.An -nosplit 655The ACPICA subsystem is developed and maintained by 656Intel Architecture Labs. 657.Pp 658The following people made notable contributions to the ACPI subsystem 659in 660.Dx : 661.An Michael Smith , 662.An Takanori Watanabe Aq Mt takawata@jp.FreeBSD.org , 663.An Mitsuru IWASAKI Aq Mt iwasaki@jp.FreeBSD.org , 664.An Munehiro Matsuda , 665.An Nate Lawson , 666the ACPI-jp mailing list at 667.Aq Mt acpi-jp@jp.FreeBSD.org , 668and many other contributors. 669.Pp 670This manual page was written by 671.An Michael Smith Aq Mt msmith@FreeBSD.org . 672.Sh BUGS 673Many BIOS versions have serious bugs that may cause system instability, 674break suspend/resume, or prevent devices from operating properly due to 675IRQ routing problems. 676Upgrade your BIOS to the latest version available from the vendor before 677deciding it is a problem with 678.Nm . 679.\".Pp 680.\"The 681.\".Nm 682.\"CPU idle power management drive conflicts with the local APIC (LAPIC) 683.\"timer. 684.\"Disable APIC mode with 685.\".Va hint.apic.0.disabled 686.\"or do not use the 687.\".Li C2 688.\"and 689.\".Li C3 690.\"states if APIC mode is enabled. 691