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62-478: The Springboard expansion slot is an expansion port for the Handspring brand of personal digital assistants (PDAs) that ran Palm OS . This socket accepted many different modules with varying functionality including cell phone telecommunications, Wi-Fi connectivity, MP3 player hardware, Global Positioning System reception, a digital camera , external storage , and software otherwise too large to fit into

124-513: A de facto standard was Altair with the Altair 8800 , developed 1974–1975, which later became a multi-manufacturer standard, the S-100 bus . Many of these computers were also passive backplane designs, where all elements of the computer, (processor, memory, and I/O) plugged into a card cage which passively distributed signals and power between the cards. Proprietary bus implementations for systems such as

186-411: A single serial RS232 port or Ethernet port. An expansion card can be installed to offer multiple RS232 ports or multiple and higher bandwidth Ethernet ports. In this case, the motherboard provides basic functionality but the expansion card offers additional or enhanced ports. One edge of the expansion card holds the contacts (the edge connector or pin header ) that fit into the slot. They establish

248-523: A PCI Bus. Generally speaking, most PCI expansion cards will function on any CPU platform which incorporates PCI bus hardware provided there is a software driver for that type. PCI video cards and any other cards that contain their own BIOS or other ROM are problematic, although video cards conforming to VESA Standards may be used for secondary monitors. DEC Alpha, IBM PowerPC, and NEC MIPS workstations used PCI bus connectors. Both Zorro II and NuBus were plug and play , requiring no hardware configuration by

310-412: A discrete GPU. Most other computer lines, including those from Apple Inc. , Tandy , Commodore , Amiga , and Atari, Inc. , offered their own expansion buses. The Amiga used Zorro II . Apple used a proprietary system with seven 50-pin-slots for Apple II peripheral cards , then later used both variations on Processor Direct Slot and NuBus for its Macintosh series until 1995, when they switched to

372-643: A few years of its arrival in 1992, PCI had largely superseded Micro Channel, EISA, and VLB. In response to the rise of EISA, IBM and thirteen Micro Channel card and peripheral manufacturers formed the Micro Channel Developers Association . This was a consortium that sought to consider and prioritize steps in the maturation of Micro Channel, as well as to explore better approaches to disseminating technical information about Micro Channel to third parties. In 1992, it reached 92 members, including IBM. Even after IBM discontinued MCA systems in 1995,

434-429: A key part of a system used for industrial process control. Expansion cards can often be installed or removed in the field, allowing a degree of user customization for particular purposes. Some expansion cards take the form of "daughterboards" that plug into connectors on a supporting system board. In personal computing , notable expansion buses and expansion card standards include the S-100 bus from 1974 associated with

496-451: A modest increase in terms of clock rate, but the greater bus width, coupled with a dedicated bus controller that utilized burst mode transfers, meant that effective throughput was up to five times higher than ISA. For faster transfers the address bus could be reused for data, further increasing the effective width of the bus. While the 10 MHz rate allowed 40 MB/s of throughput at 32-bit width, later models of RS/6000 machines increased

558-532: A new card (video, printer, memory, network, modem, etc.) the user simply plugged in the MCA card and inserted a customized floppy disk (that came with the PC) to blend the new card into the original hardware automatically, rather than bringing in an expensively trained technician who could manually make all the needed changes. All choices for interrupts (an often perplexing problem) and other changes were accomplished automatically by

620-429: A newer card, causing an error at startup. In turn, this required IBM to release updated Reference Disks (The CMOS Setup Utility) on a regular basis. A fairly complete list of known IDs is available (see External links section). To accompany these reference disks were ADF files which were read by setup which in turn provided configuration information for the card. The ADF was a simple text file, containing information about

682-522: A number of additional optional connectors for memory cards which resulted in a huge number of physically incompatible cards for bus attached memory. In time, memory moved to the CPU's local bus , thereby eliminating the problem. On the upside, signal quality was greatly improved as Micro Channel added ground and power pins and arranged the pins to minimize interference; a ground or a supply was thereby located within 3 pins of every signal. Another connector extension

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744-535: A passive adapter can be made to connect XT cards to a PLUS expansion connector. Another feature of PLUS cards is that they are stackable. Another bus that offered stackable expansion modules was the "sidecar" bus used by the IBM PCjr . This may have been electrically comparable to the XT bus; it most certainly had some similarities since both essentially exposed the 8088 CPU's address and data buses, with some buffering and latching,

806-469: A prisoner of its standards as its competitors are. Once enough IBM machines have been bought, IBM cannot make sudden changes in their basic design; what might be useful for shedding competitors would shake off even more customers. Micro Channel architecture was publicly introduced at the launch of the PS/2 range in 1987, with three out of four of the new machines featuring it. IBM had actually discreetly introduced

868-632: A second connector for extending the address and data bus over the XT, but was backward compatible; 8-bit cards were still usable in the AT 16-bit slots. Industry Standard Architecture (ISA) became the designation for the IBM AT bus after other types were developed. Users of the ISA bus had to have in-depth knowledge of the hardware they were adding to properly connect the devices, since memory addresses, I/O port addresses, and DMA channels had to be configured by switches or jumpers on

930-412: Is an expansion card that attaches to a system directly. Daughterboards often have plugs, sockets, pins or other attachments for other boards. Daughterboards often have only internal connections within a computer or other electronic devices, and usually access the motherboard directly rather than through a computer bus . Such boards are used to either improve various memory capacities of a computer, enable

992-539: Is essentially a compact version of the ISA bus. The CardBus expansion card standard is an evolution of the PC card standard to make it into a compact version of the PCI bus. The original ExpressCard standard acts like it is either a USB 2.0 peripheral or a PCI Express 1.x x1 device. ExpressCard 2.0 adds SuperSpeed USB as another type of interface the card can use. Unfortunately, CardBus and ExpressCard are vulnerable to DMA attack unless

1054-571: Is passed more efficiently. Advanced interrupt handling refers to the use of level-sensitive interrupts to handle system requests. Rather than a dedicated interrupt line, several lines can be shared to provide more possible interrupts, addressing the ISA-bus interrupt line conflict problems. All interrupt request signals were "public" on Micro Channel architecture permitting any card on the bus to function as an I/O processor for direct service of I/O device interrupts. ISA had limited all such processing to just

1116-471: Is taken for granted now, but at the time setup was a huge chore for ISA systems. POS was a simple system that included device IDs in firmware, which the drivers in the computer were supposed to interpret. (This type of software-configuration system is known as plug and play today.) The feature did not really live up to its promise; the automatic configuration was fine when it worked, but it frequently did not - resulting in an unbootable computer - and resolving

1178-624: The Apple II co-existed with multi-manufacturer standards. IBM introduced what would retroactively be called the Industry Standard Architecture (ISA) bus with the IBM PC in 1981. At that time, the technology was called the PC bus . The IBM XT , introduced in 1983, used the same bus (with slight exception). The 8-bit PC and XT bus was extended with the introduction of the IBM AT in 1984. This used

1240-672: The CP/M operating system , the 50-pin expansion slots of the original Apple II computer from 1977 (unique to Apple), IBM's Industry Standard Architecture (ISA) introduced with the IBM PC in 1981, Acorn 's tube expansion bus on the BBC Micro also from 1981, IBM's patented and proprietary Micro Channel architecture (MCA) from 1987 that never won favour in the clone market, the vastly improved Peripheral Component Interconnect (PCI) that displaced ISA in 1992, and PCI Express from 2003 which abstracts

1302-552: The Chips and Technologies P82C612 MCA interface controller; allowing MCA implementations to become a lot easier. The Micro Channel was primarily a 32-bit bus, but the system also supported a 16-bit mode designed to lower the cost of connectors and logic in Intel -based machines like the IBM PS/2 . The situation was never that simple, however, as both the 32-bit and 16-bit versions initially had

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1364-952: The IBM 9370 systems - smallest members of the System/370 range. IBM licensed the architecture to other companies for one to five percent of revenue. Tandy Corporation was the first to ship a Micro Channel-based computer, the 5000 MC, but company head John Roach said "I'm surprised anybody at all would want it"; Tandy only sold the computer, he said, because there was some demand for it. NCR Corporation adopted Micro Channel comprehensively - they designed and built high-performance personal computer, workstation and server platforms supporting it, including their own Micro Channel architecture-based logic componentry, including SCSI, graphics, networking, and audio. A small number of other manufacturers, including Apricot , Dell , Research Machines , and Olivetti adopted it, but only for part of their PC range. Despite

1426-551: The Micro Channel bus, is a proprietary 16- or 32-bit parallel computer bus publicly introduced by IBM in 1987 which was used on PS/2 and other computers until the mid-1990s. Its name is commonly abbreviated as " MCA ", although not by IBM. In IBM products, it superseded the ISA bus and was itself subsequently superseded by the PCI bus architecture. The development of Micro Channel

1488-679: The Nintendo Entertainment System and the Sega Genesis included expansion buses in some form; In the case of at least the Genesis, the expansion bus was proprietary. In fact, the cartridge slots of many cartridge-based consoles (not counting the Atari 2600 ) would qualify as expansion buses, as they exposed both read and write capabilities of the system's internal bus. However, the expansion modules attached to these interfaces, though functionally

1550-683: The PCMCIA connector, is a PCI format that attaches peripherals to the Host PCI Bus via PCI to PCI Bridge. Cardbus is being supplanted by ExpressCard format. Intel introduced the AGP bus in 1997 as a dedicated video acceleration solution. AGP devices are logically attached to the PCI bus over a PCI-to-PCI bridge. Though termed a bus, AGP usually supports only a single card at a time ( Legacy BIOS support issues). From 2005 PCI Express has been replacing both PCI and AGP. This standard, approved in 2004, implements

1612-648: The VESA Local Bus Standard, were late 1980s expansion buses that were tied but not exclusive to the 80386 and 80486 CPU bus. The PC/104 bus is an embedded bus that copies the ISA bus. Intel launched their PCI bus chipsets along with the P5 -based Pentium CPUs in 1993. The PCI bus was introduced in 1991 as a replacement for ISA. The standard (now at version 3.0) is found on PC motherboards to this day. The PCI standard supports bus bridging: as many as ten daisy-chained PCI buses have been tested. CardBus , using

1674-456: The form factor of the motherboard and case , around one to seven expansion cards can be added to a computer system. 19 or more expansion cards can be installed in backplane systems. When many expansion cards are added to a system, total power consumption and heat dissipation become limiting factors. Some expansion cards take up more than one slot space. For example, many graphics cards on the market as of 2010 are dual slot graphics cards, using

1736-886: The mezzanine of a theatre . Wavetable cards ( sample-based synthesis cards) are often mounted on sound cards in this manner. Some mezzanine card interface standards include the 400 pin FPGA Mezzanine Card (FMC); the 172 pin High-Speed Mezzanine Card (HSMC); the PCI Mezzanine Card (PMC); XMC mezzanines; the Advanced Mezzanine Card ; IndustryPacks (VITA 4), the GreenSpring Computers Mezzanine modules ; etc. Examples of daughterboard-style expansion cards include: Micro Channel architecture Micro Channel architecture , or

1798-533: The 16-bit AT bus, (embraced and renamed as ISA to avoid IBM's "AT" trademark) and manual configuration, although the VESA Local Bus (VLB) was briefly popular for Intel '486 machines. For servers the technical limitations of the old ISA were too great, and, in late 1988, the " Gang of Nine ", led by Compaq , announced a rival high-performance bus - Extended Industry Standard Architecture (EISA). This offered similar performance benefits to Micro Channel, but with

1860-655: The Micro Channel architecture in October 1986, half a year before the introduction of the IBM PS/2, as part of their "Gearbox" Industrial Computer 7552 series. These computers were rack-mountable, ruggedized, modular industrial PCs . They featured a hybrid 16-bit MCA and ISA bus, with certain ISA signal lines disabled. The use of MCA in IBM spread to the RS/6000 , AS/400 , and eventually to

1922-446: The PC reading the old configuration from the floppy disk, which made necessary changes in software, then wrote the new configuration to the floppy disk. In practice, however, this meant that the user must keep that same floppy disk matched to that PC . For a small company with a few PCs, this was annoying, but practical. But for large organizations with hundreds or even thousands of PCs, permanently matching each PC with its own floppy disk

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1984-482: The PDA's internal memory . This PDA-related article is a stub . You can help Misplaced Pages by expanding it . Expansion port Expansion cards allow the capabilities and interfaces of a computer system to be extended or supplemented in a way appropriate to the tasks it will perform. For example, a high-speed multi-channel data acquisition system would be of no use in a personal computer used for bookkeeping, but might be

2046-582: The addition of interrupts and DMA provided by Intel add-on chips, and a few system fault detection lines (Power Good, Memory Check, I/O Channel Check). Again, PCjr sidecars are not technically expansion cards, but expansion modules, with the only difference being that the sidecar is an expansion card enclosed in a plastic box (with holes exposing the connectors). Laptops are generally unable to accept most expansion cards intended for desktop computers. Consequently, several compact expansion standards were developed. The original PC Card expansion card standard

2108-430: The basic functionality of an electronic device, such as when a certain model has features added to it and is released as a new or separate model. Rather than redesigning the first model completely, a daughterboard may be added to a special connector on the main board. These usually fit on top of and parallel to the board, separated by spacers or standoffs , and are sometimes called mezzanine cards due to being stacked like

2170-401: The board for limited changes or customization. Since reliable multi-pin connectors are relatively costly, some mass-market systems such as home computers had no expansion slots and instead used a card-edge connector at the edge of the main board, putting the costly matching socket into the cost of the peripheral device. In the case of expansion of on-board capability, a motherboard may provide

2232-526: The card to match the settings in driver software. IBM's MCA bus, developed for the PS/2 in 1987, was a competitor to ISA, also their design, but fell out of favor due to the ISA's industry-wide acceptance and IBM's licensing of MCA. EISA, the 32-bit extended version of ISA championed by Compaq , was used on some PC motherboards until 1997, when Microsoft declared it a "legacy" subsystem in the PC 97 industry white-paper. Proprietary local buses (q.v. Compaq) and then

2294-432: The card's memory addressing and interrupts. Although MCA cards cost nearly double the price of comparable non-MCA cards, the marketing stressed that it was simple for any user to upgrade or add more cards to their PC, thus saving the considerable expense of a technician. In this critical area, Micro Channel architecture's biggest advantage was also its greatest disadvantage, and one of the major reasons for its demise. To add

2356-452: The computer to connect to certain kinds of networks that it previously could not connect to, or to allow for users to customize their computers for various purposes such as gaming. Daughterboards are sometimes used in computers in order to allow for expansion cards to fit parallel to the motherboard, usually to maintain a small form factor . This form are also called riser cards , or risers. Daughterboards are also sometimes used to expand

2418-408: The consortium still held meetings and maintained a catalog of MCA devices online. A number of non-PS/2 computers were manufactured between the late 1980s and early 1990s. Such third-party computers were also referred to as PS/2 clones or MCA clones . The first third-party Micro Channel–based computer was Tandy Corporation 's 5000 MC in 1988. Despite expensive research and development costs on

2480-407: The data rate to 20 MHz, and the throughput to 80 MB/s. Some higher throughput functions of the Micro Channel bus were available to RS/6000 platform only, and were not initially supported on cards operating on an Intel platform. With bus mastering , each card could talk to another directly. This allowed performance that was independent of the CPU. One potential drawback of multi-master design

2542-461: The electrical contact between the electronics on the card and on the motherboard. Peripheral expansion cards generally have connectors for external cables. In the PC-compatible personal computer, these connectors were located in the support bracket at the back of the cabinet. Industrial backplane systems had connectors mounted on the top edge of the card, opposite to the backplane pins. Depending on

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2604-506: The fact that MCA was a huge technical improvement over ISA, it soon became clear that its introduction and marketing by IBM was poorly handled. IBM had strong patents on Micro Channel architecture system features, and required Micro Channel system manufacturers to pay a licence fee - and actively pursued patents to block third parties from selling unlicensed implementations of it. The PC clone market did not want to pay royalties to IBM in order to use this new technology, and stayed largely with

2666-416: The interconnect into high-speed communication "lanes" and relegates all other functions into software protocol. Vacuum-tube based computers had modular construction, but individual functions for peripheral devices filled a cabinet, not just a printed circuit board. Processor, memory and I/O cards became feasible with the development of integrated circuits . Expansion cards make processor systems adaptable to

2728-414: The laptop has an IOMMU that is configured to thwart these attacks. One notable exception to the above is the inclusion of a single internal slot for a special reduced size version of the desktop standard. The most well known examples are Mini-PCI or Mini PCIe . Such slots were usually intended for a specific purpose such as offering "built-in" wireless networking or upgrading the system at production with

2790-518: The logical PCI protocol over a serial communication interface. PC/104(-Plus) or Mini PCI are often added for expansion on small form factor boards such as Mini-ITX . For their 1000 EX and 1000 HX models, Tandy Computer designed the PLUS expansion interface, an adaptation of the XT-bus supporting cards of a smaller form factor. Because it is electrically compatible with the XT bus (a.k.a. 8-bit ISA or XT-ISA),

2852-549: The needs of the user by making it possible to connect various types of devices, including I/O, additional memory, and optional features (such as a floating point unit ) to the central processor. Minicomputers, starting with the PDP-8 , were made of multiple cards communicating through, and powered by, a passive backplane . The first commercial microcomputer to feature expansion slots was the Micral N , in 1973. The first company to establish

2914-488: The new IRQ for a new device—if a suitable one was available—for ISA was no fun at all, and beyond many users... it is obvious why the attempt was made to move to software-arbitrated configuration, and why this was to later succeed in the form of PnP .) In November 1983 The Economist stated that the IBM PC standard's dominance of the personal computer market was not a problem because "it can help competition to flourish". The magazine predicted that IBM will soon be as much

2976-452: The on-board graphics system when needed, and allowing a single system board connector for graphics that could be upgraded. Micro Channel cards also featured a unique, 16-bit software-readable ID, which formed the basis of an early plug and play system. The BIOS and/or OS can read IDs, compare against a list of known cards, and perform automatic system configuration to suit. This led to boot failures whereby an older BIOS would not recognize

3038-411: The part of third-party manufacturers of Micro Channel computers—in part due to the expensive licensing fees incurred by IBM in order to allow legal use of the Micro Channel technology—by 1990 most MCA clones were not fully compatible with the Micro Channel architecture or expansion cards based on Micro Channel. By the time IBM was winding down the PS/2 line of personal computers (which in 1987 acted as

3100-441: The problem by manual intervention was much more difficult than configuring an ISA system, not least because the documentation for the MCA device would tend to assume that the automatic configuration would work and so did not provide the necessary information to set it up by hand, unlike ISA device documentation which by necessity provided full details (however having to physically remove and check all IRQ settings, then find and set

3162-547: The same as expansion cards, are not technically expansion cards, due to their physical form. The primary purpose of an expansion card is to provide or expand on features not offered by the motherboard. For example, the original IBM PC did not have on-board graphics or hard drive capability. In that case, a graphics card and an ST-506 hard disk controller card provided graphics capability and hard drive interface respectively. Some single-board computers made no provision for expansion cards, and may only have provided IC sockets on

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3224-582: The second slot as a place to put an active heat sink with a fan. Some cards are "low-profile" cards, meaning that they are shorter than standard cards and will fit in a lower height computer chassis such as HTPC and SFF . (There is a "low profile PCI card" standard that specifies a much smaller bracket and board area). The group of expansion cards that are used for external connectivity, such as network , SAN or modem cards, are commonly referred to as input/output cards (or I/O cards). A daughterboard , daughtercard , mezzanine board or piggyback board

3286-462: The system bus. Micro Channel bus-master-capable devices can even use the bus to talk directly to each other ( peer-to-peer ) at speeds faster than the system CPU, without any other system intervention. In theory, Micro Channel architecture systems could be expanded, like mainframes , with only the addition of intelligent masters, without periodic need to upgrade the central processor. Arbitration enhancement ensures better system throughput since control

3348-531: The system's CPU. Likewise, bus master request and grant signals were public, such that bus attached devices could monitor latency to control internal buffering for I/O processors. These features were not adopted for PCI, requiring all I/O support to come uniquely from the system board processor. The final major Micro Channel architecture improvement was POS , the Programmable Option Select , which allowed all setup to take place in software. This feature

3410-415: The twin advantage of being able to accept older ISA boards and being free from IBM's control. For several years EISA and Micro Channel battled it out in the server arena, but, in 1996, IBM effectively conceded defeat, when they themselves produced some EISA-bus servers. In 2001 IBM executive Robert Moffat said that of the company's mistakes in the PC market, "the most obvious one is Micro Channel". Within

3472-400: The user. Other computer buses were used for industrial control, instruments, and scientific systems. One specific example is HP-IB (or Hewlett Packard Interface Bus) which was ultimately standardized as IEEE-488 (aka GPIB). Some well-known historical standards include VMEbus , STD Bus , SBus (specific to Sun's SPARCStations), and numerous others. Many other video game consoles such as

3534-448: Was already investigating the use of RISC processors in desktop machines, and could, in theory, save considerable money if a single well-documented bus could be used across their entire computer lineup. It was thought that by creating a new standard, IBM would regain control of standards via the required licensing. As patents can take three years or more to be granted, however, only those relating to ISA could be licensed when Micro Channel

3596-427: Was announced. Patents on important Micro Channel features, such as Plug and Play automatic configuration, were not granted to IBM until after PCI had replaced Micro Channel in the marketplace. The overall reception was tepid and the impact of Micro Channel in the worldwide PC market was minor. The Micro Channel architecture was designed by engineer Chet Heath. A lot of the Micro Channel cards that were developed used

3658-400: Was driven by both technical and business pressures. The IBM AT bus, which later became known as the Industry Standard Architecture (ISA) bus, had a number of technical design limitations, including: In addition, it suffered from other problems: These limitations became more serious as the range of tasks and peripherals, and the number of manufacturers for IBM PC-compatibles , grew. IBM

3720-475: Was included for graphics cards . This extension was used for analog output from the video card, which was then routed through the system board to the system's own monitor output. The advantage of this was that Micro Channel system boards could have a basic VGA or MCGA graphics system on board, and higher-level graphics ( XGA or other accelerator cards) could then share the same port. The add-on cards were then able to be free of ' legacy ' VGA modes, making use of

3782-440: Was logistically unlikely or impossible. Without the original, updated floppy disk, no changes could be made to the PC's cards. After this experience repeated itself thousands of times, business leaders realized their dream scenario for upgrade simplicity did not work in the corporate world, and they sought a better process. The basic data rate of the Micro Channel was increased from ISA's 8 MHz to 10 MHz. This may have been

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3844-550: Was the possible collisions when more than one card would try to bus master, but Micro Channel included an arbitration feature to correct for these situations, and also allowed a master to use a burst-mode . Micro Channel cards had complete control for up to 12 milliseconds . This was long enough to permit the maximum number of other devices on the bus to buffer inbound data from over-runnable devices like tape and communications. Multiple bus-master support and improved arbitration mean that several such devices could coexist and share

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