A SIMM ( single in-line memory module ) is a type of memory module used in computers from the early 1980s to the early 2000s. It is a printed circuit board on which has random-access memory attached to one or both sides. It differs from a dual in-line memory module (DIMM), the most predominant form of memory module since the late 1990s, in that the contacts on a SIMM are redundant on both sides of the module. SIMMs were standardised under the JEDEC JESD-21C standard.
66-799: Most early PC motherboards ( 8088 -based PCs, XTs , and early ATs ) used socketed DIP chips for DRAM . As computer memory capacities grew, memory modules were used to save motherboard space and ease memory expansion. Instead of plugging in eight or nine single DIP chips, only one additional memory module was needed to increase the memory of the computer. SIMMs were invented in 1983 by James E. Clayton at Wang Laboratories with subsequent patents granted in 1987. Wang Laboratories litigated both patents against multiple companies . The original memory modules were built upon ceramic substrates with 64K Hitachi "flip chip" parts and had pins, i.e. single in-line package (SIP) packaging . SIMMs using pins are usually called SIP or SIPP memory modules to distinguish them from
132-468: 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: Presence detect In computing , serial presence detect ( SPD )
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
264-633: A 256-byte EEPROM is generally provided. A number of uses have been made of the remaining space. Memory generally comes with conservative timing recommendations in the SPD ROM, to ensure basic functionality on all systems. Enthusiasts often spend considerable time manually adjusting the memory timings for higher speed. Enhanced Performance Profiles is an extension of SPD, developed by Nvidia and Corsair , which includes additional information for higher-performance operation of DDR2 SDRAM , including supply voltages and command timing information not included in
330-452: A Device Type Identifier Code prefix (DTIC) with SA0-2: to read (1100) from slot 3, one uses 110 0 011 = 0x33 . With a final R/W bit it forms the 8-bit Device Select Code. Note that the semantics of slot-id is different for write-protection operations: for them they can be not passed by the SA pins at all. Before SPD, memory chips were spotted with parallel presence detect (PPD). PPD used
396-439: A card-cage case with components connected by a backplane containing 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
462-406: 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
528-407: A generic panel into a proprietary laptop. On some chips it is also a good idea to separate write protect lines so that the onboard chips do not get wiped during reprogramming. A related technique is rewriting the chip on webcams often included with many laptops as the bus speed is substantially higher and can even be modified so that 25x compatible chips can be read back for later cloning of the uEFI in
594-472: 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
660-540: A memory bank. On 386DX , 486 , and full-spec 68020 through 68060 (e.g. Atari TT, Amiga 4000, Mac II) systems (32 bit data bus), either four 30-pin SIMMs or one 72-pin SIMM are required for one memory bank. On Pentium systems (data bus width of 64 bits), two 72-pin SIMMs are required. However, some Pentium systems have support for a "half bank mode", in which the data bus would be shortened to only 32 bits to allow operation of
726-555: 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
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#1732776017252792-448: 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
858-479: A separate pin for each bit of information, which meant that only the speed and density of the memory module could be stored because of the limited space for pins. The first SPD specification was issued by JEDEC and tightened up by Intel as part of its PC100 memory specification introduced in 1998. Most values specified are in binary-coded decimal form. The most significant nibble can contain values from 10 to 15, and in some cases extends higher. In such cases,
924-412: 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
990-434: A single SIMM. Conversely, some 386 and 486 systems use what is known as "memory interleaving", which requires twice as many SIMMs and effectively doubles the bandwidth. The earliest SIMM sockets were conventional push-type sockets. These were soon replaced by ZIF sockets in which the SIMM was inserted at an angle, then tilted into an upright position. To remove one, the two metal or plastic clips at each end must be pulled to
1056-471: A total of 24 address bits, two ranks of chips, and 32-bit data output, the absolute maximum capacity is 2 = 128 MB. Pins 35, 36, 37 and 38 are not connected on non-parity SIMMs. /RAS1 and /RAS3 are only used on two-rank SIMMS: 2, 8, 32, and 128 MB. These lines are only defined on 3.3 V modules. Presence-detect signals are detailed in JEDEC standard. Several CPU cards from Great Valley Products for
1122-511: A total of 24 address bits. With an 8-bit data width, this leads to an absolute maximum capacity of 16 MB for both parity and non-parity modules (the additional redundancy-bit chip usually does not contribute to the usable capacity). Pins 26, 28 and 29 are not connected on non-parity SIMMs. Standard sizes: 1 MB, 2 MB, 4 MB, 8 MB, 16 MB, 32 MB, 64 MB, 128 MB (the standard also defines 3.3 V modules with additional address lines and up to 2 GB) With 12 address lines, which can provide
1188-433: A variety of other custom components. Similarly, the term mainboard describes 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
1254-704: 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
1320-515: 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,
1386-1090: Is "SLI-ready memory". The term "SLI-ready-memory" has caused some confusion, as it has nothing to do with SLI video . One can use EPP/SLI memory with a single video card (even a non-Nvidia card), and one can run a multi-card SLI video setup without EPP/SLI memory. An extended version, EPP 2.0, supports DDR3 memory as well. A similar, Intel -developed JEDEC SPD extension was developed for DDR3 SDRAM DIMMs, later used in DDR4 and DDR5 SDRAM as well. XMP uses bytes 176–255, which are unallocated by JEDEC, to encode higher-performance memory timings. Later, AMD developed AMP, an equivalent technology to XMP, for use in its "Radeon Memory" line of memory modules optimized for use in AMD platforms. Furthermore, motherboard developers implemented their own technologies to allow their AMD-based motherboards to read XMP profiles: MSI offers A-XMP, ASUS has DOCP (Direct Over Clock Profile), and Gigabyte has EOCP (Extended Over Clock Profile). The header contains
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#17327760172521452-595: Is a JEDEC SPD extension developed for DDR5 DIMMs to apply a one-click automatic overclocking profile to system memory. AMD EXPO-certified DIMMs include optimised timings that optimise the performance of its Zen 4 processors. Unlike Intel's closed standard XMP, the EXPO standard is open and royalty-free. It can be used on Intel platforms. At launch in September 2022, there are 15 partner RAM kits with EXPO-certification available reaching up to 6400 MT/s. A common misuse
1518-501: Is a standardized way to automatically access information about a memory module . Earlier 72-pin SIMMs included five pins that provided five bits of parallel presence detect (PPD) data, but the 168-pin DIMM standard changed to a serial presence detect to encode more information. When an ordinary modern computer is turned on, it starts by doing a power-on self-test (POST). Since about
1584-604: Is as generic SMBus readers, as the internal EEPROM on the module can be disabled once the BIOS has read it so the bus is essentially available for use. The method used is to pull low the A0,A1 lines so the internal memory shuts down, allowing the external device to access the SMBus. Once this is done, a custom Linux build or DOS application can then access the external device. A common use is recovering data from LCD panel memory chips to retrofit
1650-426: Is further divided into two physical blocks of 128 bytes each, totaling four blocks and 512 bytes. Other semantics for "special" address ranges remain the same, although write protection is now addressed by blocks and a high voltage at SA0 is now required to change its status. Annex L defines a few different layouts that can be plugged into a 512-byte (of which a maximum of 320 bytes are defined) template, depending on
1716-415: Is the main printed circuit board (PCB) in general-purpose computers and other expandable systems. It holds and allows communication between many of 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,
1782-418: Is to write information to certain memory regions to bind vendor-specific memory modules to a specific system. Fujitsu Technology Solutions is known to do this. Adding different memory module to the system usually results in a refusal or other counter-measures (like pressing F1 on every boot). This is the output of a 512 MB memory module from Micron Technologies, branded for Fujitsu-Siemens Computers, note
1848-406: 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
1914-461: Is usually rounded up and the correction is negative. Values that work this way are: The memory capacity of a module can be computed from bytes 4, 7 and 8. The module width (byte 8) divided by the number of bits per chip (byte 7) gives the number of chips per rank. That can then be multiplied by the per-chip capacity (byte 4) and the number of ranks of chips on the module (usually 1 or 2, from byte 7). The DDR4 SDRAM "Annex L" standard for SPD changes
1980-704: 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
2046-477: 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
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2112-675: The Commodore Amiga used special 64-pin SIMMs (32 bits wide, 1, 4 or 16 MB, 60 ns). Dual-ported 64-pin SIMMs were used in Apple Macintosh IIfx computers to allow overlapping read/write cycles (1, 4, 8, 16 MB, 80 ns). 72-pin SIMMs with non-standard presence detect (PD) connections. Motherboard A motherboard (also called mainboard , main circuit board , MB , base board , system board , or, in Apple computers, logic board )
2178-429: 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
2244-482: The chipset 's input/output and memory controllers, interface connectors, and other components integrated for general use. Motherboard means specifically 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
2310-442: The "FSC" string. The system BIOS rejects memory modules that don't have this information starting at offset 128h. Some Packard Bell AMD laptops also use this method, in this case the symptoms can vary but it can lead to a flashing cursor rather than a beep pattern. Incidentally this can also be a symptom of BIOS corruption as well. Though upgrading a 2 GB to a 4 GB can also lead to issues. Memory module manufacturers write
2376-460: The CAS latency has been dropped; now there are just a single set of timing parameters. Revision 1.1 lets some parameters be expressed as a "medium time base" value plus a (signed, −128 +127) "fine time base" correction. Generally, the medium time base is 1/8 ns (125 ps), and the fine time base is 1, 2.5 or 5 ps. For compatibility with earlier versions that lack the correction, the medium time base number
2442-420: 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
2508-522: 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
2574-488: The EEPROM module used. Instead of the old AT24C02-compatible 256-byte EEPROMs, JEDEC now defines a new nonstandard EE1004 type with two pages at the SMBus level each with 256 bytes. The new memory still uses the old 0x50–0x57 addresses, but two additional address at 0x36 (SPA0) and 0x37 (SPA1) are now used to receive commands to select the currently-active page for the bus, a form of bank switching . Internally each logical page
2640-641: The JEDEC SPD spec. The EPP information is stored in the same EEPROM, but in bytes 99–127, which are unused by standard DDR2 SPD. The parameters are particularly designed to fit the memory controller on the nForce 5 , nForce 6 and nForce 7 chipsets. Nvidia encourages support for EPP in the BIOS for its high-end motherboard chipsets. This is intended to provide "one-click overclocking " to get better performance with minimal effort. Nvidia's name for EPP memory that has been qualified for performance and stability
2706-511: The SDR SDRAM format. Mostly, parameter ranges are rescaled to accommodate higher speeds. The DDR2 SPD standard makes a number of changes, but is roughly similar to the above. One notable deletion is the confusing and little-used support for DIMMs with two ranks of different sizes. For cycle time fields (bytes 9, 23, 25 and 49), which are encoded in BCD , some additional encodings are defined for
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2772-549: The SPD information to the EEPROM on the module. Motherboard BIOSes read the SPD information to configure the memory controller. There exist several programs that are able to read and modify SPD information on most, but not all motherboard chipsets. Chipset-independent reading and writing of SPD information is done by accessing the memory's EEPROM directly with eeprom programmer hardware and software. A not so common use for old laptops
2838-574: The backplane. In older microprocessor-based systems, 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
2904-479: The computer uses the memory SPD data—to choose settings, selectively modify memory timings, or possibly to completely override the SPD data (see overclocking ). For a memory module to support SPD, the JEDEC standards require that certain parameters be in the lower 128 bytes of an EEPROM located on the memory module. These bytes contain timing parameters, manufacturer, serial number and other useful information about
2970-661: The early 1990s in later models of the IBM PS/2 , and later in systems based on the 486 , Pentium , Pentium Pro , early Pentium II , and contemporary/competing chips of other brands. By the mid-90s, 72-pin SIMMs had replaced 30-pin SIMMs in new-build computers, and were starting to themselves be replaced by DIMMs . Non-IBM PC computers such as UNIX workstations may use proprietary non-standard SIMMs. The Macintosh IIfx uses proprietary non-standard SIMMs with 64 pins. DRAM technologies used in SIMMs include FPM (Fast Page Mode memory, used in all 30-pin and early 72-pin modules), and
3036-413: The encodings for 1, 2 and 3 are instead used to encode 16, 17 and 18. A most significant nibble of 0 is reserved to represent "undefined". The SPD ROM defines up to three DRAM timings, for three CAS latencies specified by set bits in byte 18. First comes the highest CAS latency (fastest clock), then two lower CAS latencies with progressively lower clock speeds. The DDR DIMM SPD format is an extension of
3102-631: The event of a chip failure. This unfortunately only works on DDR3 and below, as DDR4 uses different security and can usually only be read. Its possible to use a tool like SPDTool or similar and replace the chip with one that has its WP line free so it can be altered in situ. On some chipsets the message "Incompatible SMBus driver?" may be seen so read is also prevented. Some memory modules (especially on Gaming PCs ) support RGB LEDs that are controlled by proprietary SMBus commands. This allows LED color control without additional connectors and cables. Kernel drivers from multiple manufacturers required to control
3168-414: 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
3234-519: The following data. Most importantly, it contains a "medium timebase" value MTB, as a rational number of nanoseconds (common values are 1/8, 1/12 and 1/16 ns). Many other later timing values are expressed as an integer number of MTB units. Also included in the header is the number of DIMMs per memory channel that the profile is designed to support; including more DIMMs may not work well. All data above are for DDR3 (XMP 1.1); DDR4 specs are not yet available. AMD's Extended Profiles for Overclocking (EXPO)
3300-441: The higher-performance EDO DRAM (used in later 72-pin modules). Due to the differing data bus widths of the memory modules and some processors, sometimes several modules must be installed in identical pairs or in identical groups of four to fill a memory bank. The rule of thumb is a 286 , 386SX , 68000 or low-end 68020 / 68030 (e.g. Atari Falcon, Mac LC) system (using a 16 bit wide data bus) would require two 30-pin SIMMs for
3366-410: 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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#17327760172523432-496: The mid-1990s, this process includes automatically configuring the hardware currently present. SPD is a memory hardware feature that makes it possible for the computer to know what memory is present, and what memory timings to use to access the memory. Some computers adapt to hardware changes completely automatically. In most cases, there is a special optional procedure for accessing BIOS parameters, to view and potentially make changes in settings. It may be possible to control how
3498-796: The module to just two: a clock signal and a data signal. The EEPROM shares ground pins with the RAM, has its own power pin, and has three additional pins (SA0–2) to identify the slot, which are used to assign the EEPROM a unique address in the range 0x50–0x57. Not only can the communication lines be shared among 8 memory modules, the same SMBus is commonly used on motherboards for system health monitoring tasks such as reading power supply voltages, CPU temperatures, and fan speeds. SPD EEPROMs also respond to I C addresses 0x30–0x37 if they have not been write protected, and an extension (TSE series) uses addresses 0x18–0x1F to access an optional on-chip temperature sensor. All those values are seven-bit I C addresses formed by
3564-469: The module. Devices utilizing the memory automatically determine key parameters of the module by reading this information. For example, the SPD data on an SDRAM module might provide information about the CAS latency so the system can set this correctly without user intervention. The SPD EEPROM firmware is accessed using SMBus , a variant of the I C protocol. This reduces the number of communication pins on
3630-588: The more common modules using edge connectors. The first variant of SIMMs has 30 pins and provides 8 bits of data (plus a 9th error-detection bit in parity SIMMs). They were used in AT-compatible ( 286 -based, e.g., Wang APC ), 386 -based, 486 -based, Macintosh Plus , Macintosh II , Quadra , Atari STE microcomputers, Wang VS minicomputers and Roland electronic samplers. The second variant of SIMMs has 72 pins and provides 32 bits of data (36 bits in parity and ECC versions). These appeared first in
3696-433: 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
3762-419: 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
3828-443: 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,
3894-453: The pins that encode the capacity and speed of the SIMM, so that compatible equipment can detect the properties of the SIMM. PD SIMMs can be used in equipment which does not support PD; the information is ignored. Standard SIMMs can easily be converted to support PD by fitting jumpers, if the SIMMs have solder pads to do so, or by soldering wires on. Standard sizes: 256 KB, 1 MB, 4 MB, 16 MB. 30-pin SIMMs have 12 address lines, which can provide
3960-406: 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
4026-418: The side, then the SIMM must be tilted back and pulled out (low-profile sockets reversed this convention somewhat, like SODIMMs - the modules are inserted at a "high" angle, then pushed down to become more flush with the motherboard). The earlier sockets used plastic retainer clips which were found to break, so steel clips replaced them. Some SIMMs support presence detect (PD). Connections are made to some of
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#17327760172524092-405: 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
4158-404: The tenths digit to represent some common timings exactly: The DDR3 SDRAM standard significantly overhauls and simplifies the SPD contents layout. Instead of a number of BCD-encoded nanosecond fields, some "timebase" units are specified to high precision, and various timing parameters are encoded as multiples of that base unit. Further, the practice of specifying different time values depending on
4224-507: 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
4290-467: The type of the memory module. The bit definitions are similar to DDR3. Preliminary table for DDR5, based on JESD400-5 specification. DDR5 expands the SPD table to 1024-byte. SPD of DDR5 is using the I3C bus. The JEDEC standard only specifies some of the SPD bytes. The truly critical data fits into the first 64 bytes, while some of the remainder is earmarked for manufacturer identification. However,
4356-679: 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)
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