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66-545: It is derived from I²C for communication with low-bandwidth devices on a motherboard , especially power related chips such as a laptop's rechargeable battery subsystem (see Smart Battery System and ACPI ). Other devices might include external master hosts, temperature sensor, fan or voltage sensors, lid switches, clock generator, and RGB lighting . Peripheral Component Interconnect (PCI) add-in cards may connect to an SMBus segment. A device can provide manufacturer information, indicate its model/part number, save its state for

132-502: A BIOS , as did the boot ROM on the original IBM PC, or UEFI . UEFI is a successor to BIOS that became popular after Microsoft began requiring it for a system to be certified to run Windows 8 . When the computer is powered on, the boot firmware tests and configures memory, circuitry, and peripherals. This Power-On Self Test (POST) may include testing some of the following things: Advanced Configuration and Power Interface Advanced Configuration and Power Interface ( ACPI )

198-615: A water cooling system instead of many fans. Some small form factor computers and home theater PCs designed for quiet and energy-efficient operation boast fan-less designs. This typically requires the use of a low-power CPU, as well as a careful layout of the motherboard and other components to allow for heat sink placement. A 2003 study found that some spurious computer crashes and general reliability issues, ranging from screen image distortions to I/O read/write errors, can be attributed not to software or peripheral hardware but to aging capacitors on PC motherboards. Ultimately this

264-408: A "Function Fixed Hardware (FFH) Interface", or a platform-independent hardware programming model which relies on platform-specific ACPI Machine Language (AML) provided by the original equipment manufacturer (OEM). Function Fixed Hardware interfaces are platform-specific features, provided by platform manufacturers for the purposes of performance and failure recovery. Standard Intel -based PCs have

330-408: A 4 mA sink current that cannot be driven by I²C chips unless the pull-up resistor is sized to I²C-bus levels. NXP devices have a higher power set of electrical characteristics than SMBus 1.0. The main difference is the current sink capability with V OL = 0.4 V. SMBus ‘high power’ devices and I²C-bus devices will work together if the pull-up resistor is sized for 3 mA. The SMBus clock

396-401: A PCB with expansion capabilities. As the name suggests, this board is often referred to as the mother of all components attached to it, which often include peripherals, interface cards, and daughterboards : sound cards , video cards , network cards , host bus adapters , TV tuner cards , IEEE 1394 cards, and a variety of other custom components. Similarly, the term mainboard describes

462-726: A device or processor operates (D0 and C0, respectively), it can be in one of several power-performance states . These states are implementation-dependent. P0 is always the highest-performance state, with P1 to P n being successively lower-performance states. The total number of states is device or processor dependent, but can be no greater than 16. P-states have become known as SpeedStep in Intel processors, as PowerNow! or Cool'n'Quiet in AMD processors, and as PowerSaver in VIA processors. ACPI-compliant systems interact with hardware through either

528-471: A device with a single board and no additional expansions or capability, such as controlling boards in laser printers, television sets, washing machines, mobile phones, and other embedded systems with limited expansion abilities. Prior to the invention of the microprocessor , the CPU of a digital computer consisted of multiple circuit boards in a card-cage case with components connected by a backplane containing

594-406: A different number of connections depending on its standard and form factor . A standard, modern ATX motherboard will typically have two or three PCI-Express x16 connection for a graphics card, one or two legacy PCI slots for various expansion cards, and one or two PCI-E x1 (which has superseded PCI ). A standard EATX motherboard will have two to four PCI-E x16 connection for graphics cards, and

660-422: A fixed function interface defined by Intel, which provides a set of core functionality that reduces an ACPI-compliant system's need for full driver stacks for providing basic functionality during boot time or in the case of major system failure. ACPI Platform Error Interface (APEI) is a specification for reporting of hardware errors, e.g. chipset, RAM to the operating system. ACPI defines many tables that provide

726-423: A lifetime of 3 to 4 years can be expected. However, many manufacturers deliver substandard capacitors, which significantly reduce life expectancy. Inadequate case cooling and elevated temperatures around the CPU socket exacerbate this problem. With top blowers, the motherboard components can be kept under 95 °C (203 °F), effectively doubling the motherboard lifetime. Mid-range and high-end motherboards, on

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792-555: A peripheral device. If no peripheral device containing an operating system was available, then the computer would perform tasks from other ROM stores or display an error message, depending on the model and design of the computer. For example, both the Apple II and the original IBM PC had Cassette BASIC (ROM BASIC) and would start that if no operating system could be loaded from the floppy disk or hard disk. The boot firmware in modern IBM PC compatible motherboard designs contains either

858-448: A separate component. Business PCs, workstations, and servers were more likely to need expansion cards, either for more robust functions, or for higher speeds; those systems often had fewer embedded components. Laptop and notebook computers that were developed in the 1990s integrated the most common peripherals. This even included motherboards with no upgradeable components, a trend that would continue as smaller systems were introduced after

924-424: A set of interconnected sockets into which the circuit boards are plugged. In very old designs, copper wires were the discrete connections between card connector pins, but printed circuit boards soon became the standard practice. The central processing unit (CPU), memory, and peripherals were housed on individually printed circuit boards, which were plugged into the backplane. In older microprocessor-based systems,

990-412: A set of low-speed peripherals: PS/2 keyboard and mouse , floppy disk drive , serial ports , and parallel ports . By the late 1990s, many personal computer motherboards included consumer-grade embedded audio, video, storage, and networking functions without the need for any expansion cards at all; higher-end systems for 3D gaming and computer graphics typically retained only the graphics card as

1056-443: A suspend event, report different types of errors, accept control parameters, return status over SMBus, and poll chipset registers. The SMBus is generally not user configurable or accessible. Although SMBus devices usually can't identify their functionality, a new PMBus coalition has extended SMBus to include conventions allowing that. The SMBus was defined by Intel and Duracell in 1994. It carries clock, data, and instructions and

1122-704: A variety of sizes and shapes called form factors , some of which are specific to individual computer manufacturers. However, the motherboards used in IBM-compatible systems are designed to fit various case sizes. As of 2024 , most desktop computer motherboards use the ATX standard form factor — even those found in Macintosh and Sun computers, which have not been built from commodity components. A case's motherboard and power supply unit (PSU) form factor must all match, though some smaller form factor motherboards of

1188-515: A varying number of PCI and PCI-E x1 slots. It can sometimes also have a PCI-E x4 slot (will vary between brands and models). Some motherboards have two or more PCI-E x16 slots, to allow more than 2 monitors without special hardware, or use a special graphics technology called SLI (for Nvidia ) and Crossfire (for AMD ). These allow 2 to 4 graphics cards to be linked together, to allow better performance in intensive graphical computing tasks, such as gaming, video editing, etc. In newer motherboards,

1254-402: Is a problem on the bus and that all devices must reset in order to clear this mode. Slave devices are not then allowed to hold the clock LOW too long. SMBus 1.1 and later define optional Packet Error Checking ( PEC ). In that mode, a PEC (packet error code) byte is appended at the end of each transaction. The byte is calculated as CRC-8 checksum , calculated over the entire message including

1320-553: Is an open standard that operating systems can use to discover and configure computer hardware components, to perform power management (e.g. putting unused hardware components to sleep), auto configuration (e.g. Plug and Play and hot swapping ), and status monitoring. It was first released in December 1996. ACPI aims to replace Advanced Power Management (APM), the MultiProcessor Specification , and

1386-549: Is based on Philips ' I²C serial bus protocol. Its clock frequency range is 10 kHz to 100 kHz. (PMBus extends this to 400 kHz.) Its voltage levels and timings are more strictly defined than those of I²C, but devices belonging to the two systems are often successfully mixed on the same bus. SMBus is used as an interconnect in several platform management standards including: Alert Standard Format (ASF), Desktop and mobile Architecture for System Hardware (DASH), Intelligent Platform Management Interface (IPMI). SMBus

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1452-474: Is defined from 10 to 100 kHz while I²C can be 0–100 kHz, 0–400 kHz, 0–1 MHz and 0–3.4 MHz, depending on the mode. This means that an I²C bus running at less than 10 kHz will not be SMBus compliant since the SMBus devices may time out. Many SMBus devices will however support lower frequencies. SMBus 3.0 adds 400 kHz and 1 MHz bus speeds. There are the following differences in

1518-474: Is used to access DRAM configuration information as part of serial presence detect (SPD). SMBus has grown into a wide variety of system enumeration use cases other than power management. While SMBus is derived from I²C, there are several major differences between the specifications of the two busses in the areas of electricals, timing, protocols and operating modes. When mixing devices, the I²C specification defines

1584-406: Is usually more expensive than a desktop motherboard. A CPU socket (central processing unit) or slot is an electrical component that attaches to a printed circuit board (PCB) and is designed to house a CPU (also called a microprocessor). It is a special type of integrated circuit socket designed for very high pin counts. A CPU socket provides many functions, including a physical structure to support

1650-704: The Apple II and IBM PC include only this minimal peripheral support on the motherboard. Occasionally video interface hardware was also integrated into the motherboard; for example, on the Apple II and rarely on IBM-compatible computers such as the IBM PCjr . Additional peripherals such as disk controllers and serial ports were provided as expansion cards. Given the high thermal design power of high-speed computer CPUs and components, modern motherboards nearly always include heat sinks and mounting points for fans to dissipate excess heat. Motherboards are produced in

1716-477: The Apple II and IBM PC used ROM chips mounted in sockets on the motherboard. At power-up, the central processor unit would load its program counter with the address of the Boot ROM and start executing instructions from the Boot ROM. These instructions initialized and tested the system hardware, displayed system information on the screen, performed RAM checks, and then attempts to boot an operating system from

1782-429: The M.2 slots are for SSD and/or wireless network interface controller . Motherboards are generally air cooled with heat sinks often mounted on larger chips in modern motherboards. Insufficient or improper cooling can cause damage to the internal components of the computer, or cause it to crash . Passive cooling , or a single fan mounted on the power supply , was sufficient for many desktop computer CPU's until

1848-565: The Plug and Play BIOS (PnP) Specification. ACPI brings power management under the control of the operating system, as opposed to the previous BIOS-centric system that relied on platform-specific firmware to determine power management and configuration policies. The specification is central to the Operating System-directed configuration and Power Management ( OSPM ) system. ACPI defines hardware abstraction interfaces between

1914-662: The USB ;3.0 support, logical processor idling support, and x2APIC support. Initially ACPI is exclusive to x86 architecture; Revision 5.0 of the ACPI specification was released in December 2011, which added the ARM architecture support. The revision 5.1 was released in July 2014. The latest specification revision is 6.5, which was released in August 2022. Microsoft's Windows 98

1980-708: The ACPI tables. To make use of the ACPI tables, the operating system must have an interpreter for the AML bytecode. A reference AML interpreter implementation is provided by the ACPI Component Architecture (ACPICA). At the BIOS development time, AML bytecode is compiled from the ASL (ACPI Source Language) code. The ACPI Component Architecture ( ACPICA ), mainly written by Intel's engineers, provides an open-source platform-independent reference implementation of

2046-603: The Address Resolution Protocol), causing link interruptions that break Management Component Transport Protocol and other protocols when the Mux switches targets. To solve this problem, SNIA's Enterprise and Data Center Standard Form Factor version 3.1 (January 2023) describes a way to use I3C basic over the PCIe two-wire interface. NVM Express 2.1 (August 2024) is also reworded to allow the use of I3C, "to match

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2112-535: The BIOS date is after January 1, 1999. Similarly, Linux kernel 2.6 may not use ACPI if the BIOS date is before January 1, 2001. Linux-based operating systems can provide handling of ACPI events via acpid. Once an OSPM-compatible operating system activates ACPI, it takes exclusive control of all aspects of power management and device configuration. The OSPM implementation must expose an ACPI-compatible environment to device drivers, which exposes certain system, device and processor states. The ACPI Specification defines

2178-518: The CPU and some support circuitry would fit on a single CPU board, with memory and peripherals on additional boards, all plugged into the backplane. The ubiquitous S-100 bus of the 1970s is an example of this type of backplane system. The most popular computers of the 1980s such as the Apple II and IBM PC had published schematic diagrams and other documentation which permitted rapid reverse engineering and third-party replacement motherboards. Usually intended for building new computers compatible with

2244-420: The CPU series and speed. With the steadily declining costs and size of integrated circuits , it is now possible to include support for many peripherals on the motherboard. By combining many functions on one PCB , the physical size and total cost of the system may be reduced; highly integrated motherboards are thus especially popular in small form factor and budget computers. A typical motherboard will have

2310-471: The CPU, support for a heat sink, facilitating replacement (as well as reducing cost), and most importantly, forming an electrical interface both with the CPU and the PCB. CPU sockets on the motherboard can most often be found in most desktop and server computers (laptops typically use surface mount CPUs), particularly those based on the Intel x86 architecture. A CPU socket type and motherboard chipset must support

2376-462: The I²C multi-master mode. SMBus devices are supported by FreeBSD , OpenBSD , NetBSD , DragonFly BSD , Linux , Windows 98 and newer and Windows CE . DDR5 introduces I3C for its presence detect communication, replacing SMBus. PCI express devices commonly use SMBus as a "out-of-band management port". However, device vendors frequently use SMBus multiplexers (Mux) to manage address clashes (which are in turn caused by them not implementing

2442-560: The ability to generate the not acknowledge after the transfer of each byte and before the completion of the transaction. This is important because SMBus does not provide any other resend signaling. This difference in the use of the NACK signaling has implications on the specific implementation of the SMBus port, especially in devices that handle critical system data such as the SMBus host and the SBS components. Each message transaction on SMBus follows

2508-476: The address and read/write bit. The polynomial used is x+x+x+1 (the CRC-8- ATM HEC algorithm, initialized to zero). The SMBus has an extra optional shared interrupt signal called SMBALERT#, which can be used by slaves to tell the host to ask its slaves about events of interest. SMBus also defines a less common "Host Notify Protocol", providing similar notifications but passing more data and building on

2574-598: The bus. I²C can be a ‘DC’ bus, meaning that a slave device stretches the master clock when performing some routine while the master is accessing it. This will notify to the master that the slave is busy but does not want to lose the communication. The slave device will allow continuation after its task is complete. There is no limit in the I²C-bus protocol as to how long this delay can be, whereas for an SMBus system, it would be limited to 35 ms. The SMBus protocol just assumes that if something takes too long, then it means that there

2640-672: The computer to have an ACPI-compliant BIOS, and since Windows 8 , the S0ix/Modern Standby state was implemented. Windows operating systems use acpi.sys to access ACPI events. The 2.4 series of the Linux kernel had only minimal support for ACPI, with better support implemented (and enabled by default) from kernel version 2.6.0 onwards. Old ACPI BIOS implementations tend to be quite buggy, and consequently are not supported by later operating systems. For example, Windows 2000 , Windows XP , and Windows Server 2003 only use ACPI if

2706-498: The context of motherboard PCI Express slots, the PCIe Electromechanical Specification expects ARP to be provided for the SMBus pins. However, because ARP is marked "optional" in the SMBus specification, it's commonly left unimplemented. SMBus has a time-out feature which resets devices if a communication takes too long. This explains the minimum clock frequency of 10 kHz to prevent locking up

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2772-425: The crucial electronic components of a system, such as the central processing unit (CPU) and memory , and provides connectors for other peripherals . Unlike a backplane , a motherboard usually contains significant sub-systems, such as the central processor, the chipset 's input/output and memory controllers, interface connectors, and other components integrated for general use. Motherboard means specifically

2838-499: The device's firmware (e.g. BIOS , UEFI ), the computer hardware components, and the operating systems . Internally, ACPI advertises the available components and their functions to the operating system kernel using instruction lists (" methods ") provided through the system firmware ( UEFI or BIOS ), which the kernel parses. ACPI then executes the desired operations written in ACPI Machine Language (such as

2904-414: The exemplars, many motherboards offered additional performance or other features and were used to upgrade the manufacturer's original equipment. During the late 1980s and early 1990s, it became economical to move an increasing number of peripheral functions onto the motherboard. In the late 1980s, personal computer motherboards began to include single ICs (also called Super I/O chips) capable of supporting

2970-427: The following four global "Gx" states and six sleep "Sx" states for an ACPI-compliant computer system: The specification also defines a Legacy state: the state of an operating system which does not support ACPI. In this state, the hardware and power are not managed via ACPI, effectively disabling ACPI. The device states D0 – D3 are device dependent: The CPU power states C0 – C3 are defined as follows: While

3036-707: The format of one of the defined SMBus protocols. The SMBus protocols are a subset of the data transfer formats defined in the I²C specifications. I²C devices that can be accessed through one of the SMBus protocols are compatible with the SMBus specifications. I²C devices that do not adhere to these protocols cannot be accessed by standard methods as defined in the SMBus and Advanced Configuration and Power Interface (ACPI) specifications. The SMBus uses I²C hardware and I²C hardware addressing, but adds second-level software for building special systems. In particular its specifications include an Address Resolution Protocol that can make dynamic address allocations. Dynamic reconfiguration of

3102-437: The hardware and software allow bus devices to be ‘hot-plugged’ and used immediately, without restarting the system. The devices are recognized automatically and assigned unique addresses. This advantage results in a plug-and-play user interface. In both those protocols there is a very useful distinction made between a System Host and all the other devices in the system that can have the names and functions of masters or slaves. In

3168-504: The initialization of hardware components) using an embedded minimal virtual machine . Intel , Microsoft and Toshiba originally developed the standard, while HP , Huawei and Phoenix also participated later. In October 2013, ACPI Special Interest Group (ACPI SIG), the original developers of the ACPI standard, agreed to transfer all assets to the UEFI Forum , in which all future development will take place. The latest version of

3234-431: The input levels to be 30% and 70% of the supply voltage V DD , which may be 5 V, 3.3 V, or some other value. Instead of relating the bus input levels to V DD , SMBus defines them to be fixed at 0.8 and 2.1 V. SMBus 2.0 supports V DD ranging from 3 to 5 V. SMBus 3.0 supports V DD ranging from 1.8 to 5 V and V IH = 1.35 V. SMBus 2.0 defines a ‘High Power’ class that includes

3300-575: The interface between an ACPI-compliant operating system and system firmware ( BIOS or UEFI ). This includes RSDP, RSDT, XSDT, FADT, FACS, DSDT, SSDT, MADT, and MCFG, for example. The tables allow description of system hardware in a platform-independent manner, and are presented as either fixed-formatted data structures or in AML. The main AML table is the DSDT (differentiated system description table). The AML can be decompiled by tools like Intel's iASL (open-source, part of ACPICA) for purposes like patching

3366-460: The late 1990s; since then, most have required CPU fans mounted on heat sinks , due to rising clock speeds and power consumption. Most motherboards have connectors for additional computer fans and integrated temperature sensors to detect motherboard and CPU temperatures and controllable fan connectors which the BIOS or operating system can use to regulate fan speed. Alternatively computers can use

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3432-433: The motherboard cooling and monitoring solutions are usually based on a super I/O chip or an embedded controller . Motherboards contain a ROM (and later EPROM , EEPROM , NOR flash ) that stores firmware that initializes hardware devices and boots an operating system from a peripheral device . The terms bootstrapping and boot come from the phrase "lifting yourself by your bootstraps". Microcomputers such as

3498-419: The motherboard. Other components such as external storage , controllers for video display and sound , and peripheral devices may be attached to the motherboard as plug-in cards or via cables; in modern microcomputers, it is increasingly common to integrate some of these peripherals into the motherboard itself. An important component of a motherboard is the microprocessor's supporting chipset , which provides

3564-458: The new conventions used by SNIA SFF TA's EDSFF and PCI-SIG specifications for I3C". Motherboard A motherboard (also called mainboard , main circuit board , MB , base board , system board , or, in Apple computers, logic board ) is the main printed circuit board (PCB) in general-purpose computers and other expandable systems. It holds and allows communication between many of

3630-673: The operating system–related ACPI code. The ACPICA code is used by Linux, Haiku , ArcaOS and FreeBSD , which supplement it with their operating-system specific code. The first revision of the ACPI specification was released in December 1996, supporting 16, 24 and 32-bit addressing spaces. It was not until August 2000 that ACPI received 64-bit address support as well as support for multiprocessor workstations and servers with revision 2.0. In 1999, then Microsoft CEO Bill Gates stated in an e-mail that Linux would benefit from ACPI without them having to do work and suggested to make it Windows-only. In September 2004, revision 3.0

3696-443: The other hand, use solid capacitors exclusively. For every 10 °C less, their average lifespan is multiplied approximately by three, resulting in a 6-times higher lifetime expectancy at 65 °C (149 °F). These capacitors may be rated for 5000, 10000 or 12000 hours of operation at 105 °C (221 °F), extending the projected lifetime in comparison with standard solid capacitors. In desktop PCs and notebook computers,

3762-406: The same family will fit larger cases. For example, an ATX case will usually accommodate a microATX motherboard. Laptop computers generally use highly integrated, miniaturized, and customized motherboards. This is one of the reasons that laptop computers are difficult to upgrade and expensive to repair. Often the failure of one laptop component requires the replacement of the entire motherboard, which

3828-461: The standard 6.5 was released in August 2022. The firmware-level ACPI has three main components: the ACPI tables, the ACPI BIOS, and the ACPI registers. The ACPI BIOS generates ACPI tables and loads ACPI tables into main memory . Much of the firmware ACPI functionality is provided in bytecode of ACPI Machine Language (AML), a Turing-complete , domain-specific low-level language , stored in

3894-405: The supporting interfaces between the CPU and the various buses and external components. This chipset determines, to an extent, the features and capabilities of the motherboard. Modern motherboards include: Additionally, nearly all motherboards include logic and connectors to support commonly used input devices, such as USB for mouse devices and keyboards . Early personal computers such as

3960-846: The tables for expanding OS compatibility. The Root System Description Pointer (RSDP) is located in a platform-dependent manner, and describes the rest of the tables. A custom ACPI table called the Windows Platform Binary Table (WPBT) is used by Microsoft to allow vendors to add software into the Windows OS automatically. Some vendors, such as Lenovo , have been caught using this feature to install harmful software such as Superfish . Samsung shipped PCs with Windows Update disabled. Windows versions older than Windows 7 do not support this feature, but alternative techniques can be used. This behavior has been compared to rootkits . In November 2003, Linus Torvalds —author of

4026-425: The transfer, that it cannot receive any more data bytes. I²C specifies that the device may indicate this by generating the not acknowledge on the first byte to follow. Other than to indicate a slave's device-busy condition, SMBus also uses the NACK mechanism to indicate the reception of an invalid command or datum. Since such a condition may occur on the last byte of the transfer, it is required that SMBus devices have

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4092-507: The turn of the century (like the tablet computer and the netbook ). Memory, processors, network controllers, power source, and storage would be integrated into some systems. A motherboard provides the electrical connections by which the other components of the system communicate. Unlike a backplane, it also contains the central processing unit and hosts other subsystems and devices. A typical desktop computer has its microprocessor , main memory , and other essential components connected to

4158-467: The use of the NACK bus signaling: In I²C, a slave receiver is allowed to not acknowledge the slave address, if for example it's unable to receive because it's performing some real time task. SMBus requires devices to acknowledge their own address always, as a mechanism to detect a removable device's presence on the bus (battery, docking station, etc.) I²C specifies that a slave device, although it may acknowledge its own address, may decide, some time later in

4224-465: Was released, bringing to the ACPI specification support for SATA interfaces, PCI Express bus, multiprocessor support for more than 256 processors, ambient light sensors and user-presence devices, as well as extending the thermal model beyond the previous processor-centric support. Released in June 2009, revision 4.0 of the ACPI specification added various new features to the design; most notable are

4290-679: Was shown to be the result of a faulty electrolyte formulation, an issue termed capacitor plague . Modern motherboards use electrolytic capacitors to filter the DC power distributed around the board. These capacitors age at a temperature-dependent rate, as their water based electrolytes slowly evaporate. This can lead to loss of capacitance and subsequent motherboard malfunctions due to voltage instabilities. While most capacitors are rated for 2000 hours of operation at 105 °C (221 °F), their expected design life roughly doubles for every 10 °C (18 °F) below this. At 65 °C (149 °F)

4356-591: Was the first operating system to implement ACPI, but its implementation was somewhat buggy or incomplete, although some of the problems associated with it were caused by the first-generation ACPI hardware. Other operating systems, including later versions of Windows , macOS (x86 macOS only), eComStation , ArcaOS , FreeBSD (since FreeBSD 5.0 ), NetBSD (since NetBSD 1.6 ), OpenBSD (since OpenBSD 3.8 ), HP-UX , OpenVMS , Linux , GNU/Hurd and PC versions of Solaris , have at least some support for ACPI. Some newer operating systems, like Windows Vista , require

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