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74-470: Incorporating the PCI Express bus within the industry proven PC/104 architecture brings many advantages for embedded applications including fast data transfer, low cost due to PC/104’s unique self-stacking bus, high reliability due to PC/104’s inherent ruggedness, and long-term sustainability. There are two versions of the specification that are complementary. The main difference is that Type 2 replaces

148-936: A Board Support Package is usually provided by the manufacturer for the supported operating system(s). When printing "PC/104" or its variants, it is common for the forward slash or dashes to be omitted. PC/104 may be abbreviated as PC104, PCI-104 abbreviated as PCI104, etc. Additionally, it is common for PC/104- Plus to be abbreviated with a plus sign (e.g. PC104+). Such abbreviations are not officially recognized in any PC/104 Consortium specifications or literature, however they have been in use for some time. PC/104 systems often require small, non-volatile storage, such as that afforded by compact flash and solid state disk (SSD) devices. These are often more popular than mechanical (rotating) hard drives. Compared to rotating disks, flash-based storage devices have limited lifetimes in terms of write cycles, but they are faster and draw less power. Additionally, their compactness and physical durability

222-724: A 16-bit transfer size, signal timing in the PIO modes and the interrupt and DMA mechanisms. The PC/XT-bus is an eight- bit ISA bus used by Intel 8086 and Intel 8088 systems in the IBM PC and IBM PC XT in the 1980s. Among its 62 pins were demultiplexed and electrically buffered versions of the 8 data and 20 address lines of the 8088 processor, along with power lines, clocks, read/write strobes, interrupt lines, etc. Power lines included −5 V and ±12 V in order to directly support pMOS and enhancement mode nMOS circuits such as dynamic RAMs among other things. The XT bus architecture uses

296-441: A CPU board, power supply board, and one or more peripheral boards. The maximum number of boards supported by a PC/104 stack will depend on which buses are used by the peripheral boards. Regardless of the buses used, the maximum number of boards of a PC/104 stack may be limited due to size, weight, and power restrictions for the target application. When stacking PC/104 boards together, mechanical interference between adjacent boards

370-481: A PC/104 system (Serial Ports, USB, Ethernet, VGA, etc.) are typically supported via the native drivers built into the operating system. Certain peripheral boards, such as data acquisition may require special drivers from the board manufacturer. From a software development perspective, there is little difference between compiling software for a desktop PC or compiling for an x86 PC/104 stack. Software can be developed using standard x86 compilers (e.g. Visual Studio if

444-496: A PCI-104 expansion bus. The PC/104 Consortium specifications define a variety a computer buses, all of which derive from the ISA, PCI, and PCI Express buses found in a desktop PC. The original PC/104 bus derives from the ISA bus . It includes all the signals found on the ISA bus, with additional ground pins added to ensure bus integrity. Signal timing and voltage levels are identical to

518-578: A PCI/104-Express peripheral module will communicate on the PCIe bus only; the PCI connector is simply a pass-through connector for stackability. A PC/104-Express peripheral module may not be used with a PCI-104 or PC/104- Plus CPU board (unless an ISA bridge device is used). PCI/104-Express incorporates link shifting, which eliminates the need for the PCI slot selection switches/jumpers found on PCI-104 and PC/104- Plus peripherals. Some peripheral boards re-populate

592-524: A few unique signal lines specific to ATA/IDE hard disks (such as the Cable Select/Spindle Sync. line.) In addition to the physical interface channel, ATA goes beyond and far outside the scope of ISA by also specifying a set of physical device registers to be implemented on every ATA (IDE) drive and a full set of protocols and device commands for controlling fixed disk drives using these registers. The ATA device registers are accessed using

666-529: A more rugged mounting than slot boards found in desktop PCs. The compact board size further contributes to the ruggedness of the form factor by reducing the possibility of PCB flexing under shock and vibration. A typical PC/104 system (commonly referred to as a "stack") will include a CPU board , power supply board, and one or more peripheral boards, such as a data acquisition module, GPS receiver, or Wireless LAN controller. A wide array of peripheral boards are available from various vendors. Users may design

740-453: A second 8259 PIC (connected to one of the lines of the first) and 4 × 16-bit DMA channels, as well as control lines to select 8- or 16-bit transfers. The 16-bit AT bus slot originally used two standard edge connector sockets in early IBM PC/AT machines. However, with the popularity of the AT architecture and the 16-bit ISA bus, manufacturers introduced specialized 98-pin connectors that integrated

814-530: A separate clock generator, or a clock divider which either fixed the ISA bus frequency at 4, 6, or 8 MHz or allowed the user to adjust the frequency via the BIOS setup. When used at a higher bus frequency, some ISA cards (certain Hercules-compatible video cards, for instance), could show significant performance improvements. Memory address decoding for the selection of 8 or 16-bit transfer mode

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888-602: A single Intel 8259 PIC , giving eight vectorized and prioritized interrupt lines. It has four DMA channels originally provided by the Intel 8237 . Three of the DMA channels are brought out to the XT bus expansion slots; of these, 2 are normally already allocated to machine functions (diskette drive and hard disk controller): The PC/AT-bus , a 16- bit (or 80286-) version of the PC/XT bus,

962-456: A stack that incorporates boards from multiple vendors. The overall height, weight, and power consumption of the stack can vary depending on the number of boards that are used. PC/104 is sometimes referred to as a "stackable PC", as most of the architecture derives from the desktop PC. The majority of PC/104 CPU boards are x86 compatible and include standard PC interfaces such as Serial Ports , USB , Ethernet , and VGA . A x86 PC/104 system

1036-762: A team led by Mark Dean at IBM as part of the IBM PC project in 1981. It was an 8-bit bus based on the I/O bus of the IBM System/23 Datamaster system - it used the same physical connector, and a similar signal protocol and pinout. A 16-bit version, the IBM AT bus, was introduced with the release of the IBM PC/AT in 1984. The AT bus was a mostly backward-compatible extension of the PC bus—the AT bus connector

1110-603: A time, but this allowed for greater flexibility. The AT Attachment (ATA) hard disk interface is directly descended from the 16-bit ISA of the PC/AT. ATA has its origins in the IBM Personal Computer Fixed Disk and Diskette Adapter, the standard dual-function floppy disk controller and hard disk controller card for the IBM PC AT; the fixed disk controller on this card implemented the register set and

1184-418: Is a concern. The mechanical interference issues listed above can often be addressed with a Bus Spacer, which allows additional room between the boards. However, Bus Spacers increase overall stack height, and may not be suitable for space-constrained applications. It may also be possible to re-arrange the boards in the stack to remove the interference. Another option is to modify the offending boards to remove

1258-454: Is a derivative of the ISA bus, utilizing the same signal lines with different connectors. The LPC bus has replaced the ISA bus as the connection to the legacy I/O devices on current motherboards; while physically quite different, LPC looks just like ISA to software, so the peculiarities of ISA such as the 16 MiB DMA limit (which corresponds to the full address space of the Intel 80286 CPU used in

1332-530: Is equipped with two ISA slots. It was marketed to industrial and military users who had invested in expensive specialized ISA bus adaptors, which were not available in PCI bus versions. Similarly, ADEK Industrial Computers released a modern motherboard in early 2013 for Intel Core i3/i5/i7 processors, which contains one (non-DMA) ISA slot. Also, MSI released a modern motherboard with one ISA slot in 2020. The PC/104 bus, used in industrial and embedded applications,

1406-476: Is incompatible with PC/104 peripheral module. However, PCI-104 and PC/104- Plus are compatible, since they both utilize the PCI bus. Most PC/104- Plus boards can be manufactured as PCI-104 by simply not populating the PC/104 connector. PCI-104 utilizes the same PCI Slot Number selection scheme as PC/104- Plus . Each device must be assigned to a unique slot number. The PCI/104-Express specification incorporates

1480-402: Is incompatible with Type 2 peripherals, or vice versa. The specification requires the system to remain in reset and not boot in the case of a Type mismatch (no physical damage will occur). Universal peripheral boards may be used with either Type 1 or Type 2 pinouts. Because the PCIe bus connector is surface-mount, not through-hole, it is also possible for a board to use different bus pinouts on

1554-513: Is necessary to specify the PCI Slot Number of a peripheral board when it is installed. This is commonly set by a rotary switch , DIP switch , or jumpers on the peripheral board. Each PCI peripheral board in the system must have the PCI Slot Number set to a unique value. Failure to do so may cause erratic system behavior. The peripheral closest to the CPU should be set for the first slot,

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1628-414: Is now fairly hard to find. Some XT-IDE adapters were available as 8-bit ISA cards, and XTA sockets were also present on the motherboards of Amstrad 's later XT clones as well as a short-lived line of Philips units. The XTA pinout was very similar to ATA, but only eight data lines and two address lines were used, and the physical device registers had completely different meanings. A few hard drives (such as

1702-403: Is often better-suited to rugged PC/104 applications; the size of magnetic hard drives can be cumbersome and their many delicate parts are more susceptible to failure in harsh environments. Industry Standard Architecture Industry Standard Architecture ( ISA ) is the 16-bit internal bus of IBM PC/AT and similar computers based on the Intel 80286 and its immediate successors during

1776-502: Is somewhat smaller than a desktop PC motherboard at 3.550 × 3.775 inches (90 × 96 mm). Unlike other popular computer form factors such as ATX , which rely on a motherboard or backplane , PC/104 boards are stacked on top of each other like building blocks. The PC/104 specification defines four mounting holes at the corners of each module, which allow the boards to be fastened to each other using standoffs . The stackable bus connectors and use of standoffs provides

1850-506: Is usually capable of standard PC operating system such as DOS, Windows, or Linux. However, it is also quite common to use a real-time operating system , such as VxWorks . The PC/104 bus and form factor was originally devised by Ampro in 1987 (led by CTO Rick Lehrbaum), and later standardized by the PC/104 Consortium in 1992. An IEEE standard corresponding to PC/104 was drafted as IEEE P996.1, but never ratified. In 1997,

1924-496: The Extended Industry Standard Architecture (EISA) and the later VESA Local Bus (VLB). VLB used some electronic parts originally intended for MCA because component manufacturers already were equipped to manufacture them. Both EISA and VLB were backward-compatible expansions of the AT (ISA) bus. Users of ISA-based machines had to know special information about the hardware they were adding to

1998-547: The PCI Express bus (PCIe) in addition to the previous-generation PCI bus. The specification defines a 156-pin surface mount connector for the PCI Express signals. The new connector occupies the same board location as the legacy PC/104 ISA connector. In addition to PCI Express, the specifications also defines pins on the connector for additional modern computer buses, such as USB , SATA , and LPC . The PCI/104-Express specification currently defines two possible pinouts for

2072-490: The PCI bus , in addition to the ISA bus of the PC/104 standard. The name is derived from its origin: a PC/104- Plus module has a PC/104 connector (ISA) plus a PCI connector. The standard defines a 120-pin connector for the PCI bus, located on the opposite side of the board from the PC/104 connector. PC/104- Plus CPU boards provide active communication on both buses, and are capable of communicating with both ISA and PCI peripheral cards. On PC/104- Plus peripheral modules,

2146-467: The Seagate ST351A/X) could support either type of interface, selected with a jumper. Many later AT (and AT successor) motherboards had no integrated hard drive interface but relied on a separate hard drive interface plugged into an ISA/EISA/VLB slot. There were even a few 80486-based units shipped with MFM/RLL interfaces and drives instead of the increasingly common AT-IDE. Commodore built

2220-476: The "104" name to distinguish the form factor from the legacy PC/104 bus. EBX (Embedded Board eXpandable) is a single board computer form factor, 5.75 × 8 in (146 × 203 mm). The EBX form factor applies to the CPU board , but supports PC/104 form factor peripheral boards for expansion. The original EBX specifications allowed for the PC/104, PC/104- Plus , and PCI-104 buses. EBX Express adds

2294-451: The 104 pins on the interboard connector ( ISA ) in the original PC/104 specification and has been retained in subsequent revisions, despite changes to connectors. PC/104 is intended for specialized environments where a small, rugged computer system is required. The standard is modular, and allows consumers to stack together boards from a variety of COTS manufacturers to produce a customized embedded system. The original PC/104 form factor

PCI/104-Express - Misplaced Pages Continue

2368-420: The 16-bit version. Since PC/104 is based on the ISA bus, it is often necessary to set the base address , IRQ , and DMA channel when installing a peripheral board. This is usually accomplished via the use of jumpers or DIP switches on the peripheral board. Failure to configure the peripheral correctly can cause a resource conflict and lead to erratic behavior. The PC/104- Plus standard adds support for

2442-523: The 1980s. The bus was (largely) backward compatible with the 8-bit bus of the 8088 -based IBM PC , including the IBM PC/XT as well as IBM PC compatibles . Originally referred to as the PC bus (8-bit) or AT bus (16-bit), it was also termed I/O Channel by IBM. The ISA term was coined as a retronym by IBM PC clone manufacturers in the late 1980s or early 1990s as a reaction to IBM attempts to replace

2516-470: The 8-bit version as a buffered interface to the motherboard buses of the Intel 8088 (16/8 bit) CPU in the IBM PC and PC/XT, augmented with prioritized interrupts and DMA channels. The 16-bit version was an upgrade for the motherboard buses of the Intel 80286 CPU (and expanded interrupt and DMA facilities) used in the IBM AT, with improved support for bus mastering. The ISA bus was therefore synchronous with

2590-615: The AT bus structure were and still are used in ATA/IDE , the PCMCIA standard, CompactFlash , the PC/104 bus, and internally within Super I/O chips. Even though ISA disappeared from consumer desktops many years ago, it is still used in industrial PCs , where certain specialized expansion cards that never transitioned to PCI and PCI Express are used. The original PC bus was developed by

2664-407: The AT bus with its new and incompatible Micro Channel architecture . The 16-bit ISA bus was also used with 32-bit processors for several years. An attempt to extend it to 32 bits, called Extended Industry Standard Architecture (EISA), was not very successful, however. Later buses such as VESA Local Bus and PCI were used instead, often along with ISA slots on the same mainboard . Derivatives of

2738-527: The AT bus's performance but in 1987, IBM replaced the AT bus with its proprietary Micro Channel Architecture (MCA). MCA overcame many of the limitations then apparent in ISA but was also an effort by IBM to regain control of the PC architecture and the PC market. MCA was far more advanced than ISA and had many features that would later appear in PCI. However, MCA was also a closed standard whereas IBM had released full specifications and circuit schematics for ISA. Computer manufacturers responded to MCA by developing

2812-451: The ATA standard (up to 133 MB/s for ATA-6, the latest.) In most forms, ATA ran much faster than ISA, provided it was connected directly to a local bus (e.g. southbridge-integrated IDE interfaces) faster than the ISA bus. Before the 16-bit ATA/IDE interface, there was an 8-bit XT-IDE (also known as XTA) interface for hard disks. It was not nearly as popular as ATA has become, and XT-IDE hardware

2886-410: The CPU clock of the 80286 in IBM PC/AT computers, which was 6 MHz in the first models and 8 MHz in later models. The IBM RT PC also used the 16-bit bus. ISA was also used in some non-IBM compatible machines such as Motorola 68k -based Apollo (68020) and Amiga 3000 (68030) workstations, the short-lived AT&T Hobbit and the later PowerPC -based BeBox . Companies like Dell improved

2960-402: The CPU clock until sophisticated buffering methods were implemented by chipsets to interface ISA to much faster CPUs. ISA was designed to connect peripheral cards to the motherboard and allows for bus mastering . Only the first 16 MB of main memory is addressable. The original 8-bit bus ran from the 4.77 MHz clock of the 8088 CPU in the IBM PC and PC/XT. The original 16-bit bus ran from

3034-612: The Form Factors listed below, it is possible for a non-standard or proprietary form factor to incorporate one of the PC/104 Bus Structures for expandability. Note the term "PC/104" is often used interchangeably to refer to either the Bus Structure or Form Factor. This can be a source of confusion. For example, a product datasheet may refer to a board as "PC/104" due to its size and shape when it in fact has

PCI/104-Express - Misplaced Pages Continue

3108-567: The I/O connector area. The extended PCB "wings" is not addressed in the specification, generally does not cause mechanical issues as long as the overall PCB + I/O connector overhang is within the maximum allowable dimensions of 4.550 × 4.393 inches (116 × 112 mm). The dimensions were originally defined in the PC/104 Specification, and as a result the form factor is still commonly referred to as "PC/104". The PCI/104-Express and PCIe/104 Specification introduced

3182-472: The ISA bus, with lower current requirements. The PC/104 specification defines two versions of the bus, 8-bit or 16-bit. The 8-bit version corresponds to the IBM XT and consists of 64 pins. The 16-bit version corresponds to the IBM AT and adds 40 additional pins, bringing the total to 104 (hence the name "PC/104"). The signals marked J1/P1 are found on both versions, while the signals of J2/P2 are found only on

3256-495: The PC/104 Consortium define multiple of Bus Structures (ISA, PCI, PCI Express) and Form Factors (104, EBX, EPIC). Bus Structure defines the location and pinout of the bus connector(s). Form Factor refers to size and shape of the board. It is possible to find one of the PC/104 stackable expansion buses on a number of different form factors. While most commercially available products using the Bus Structures will comply with

3330-506: The PC/104 Consortium introduced a newer standard based on the PCI bus . A PCI Express -based standard was introduced in 2008. PC/104-related specifications are controlled by the PC/104 Consortium. There are currently 47 members of the Consortium. All specifications published by the Consortium are freely available. Membership in the Consortium is not required to design and manufacture a PC/104 board. The specifications released by

3404-433: The PC/104 connector is simply a passive connector for stackability; the module actively communicates on the PCI bus only. As a corollary, a PC/104- Plus peripheral module may not be used with a PC/104 CPU board. However, a PC/104- Plus CPU board may be used with a PC/104 peripheral module. Since PC/104- Plus is based on PCI, there is no need to set a Base Address, IRQ, or DMA channel on the peripheral boards. However, it

3478-503: The PC/104 system is running Windows). There is typically no need for specialized development tools, such as cross compilers , Board Support Packages , or JTAG debuggers . This is a significant departure from non-x86 embedded system platforms, which often require a development toolchain from the board manufacturer. Non-x86 PC/104 CPU boards based on ARM or PowerPC are also commercially available. However, such boards are not capable of running off-the-shelf PC software. In these cases,

3552-490: The PCI Express x16 link with SATA, USB 3.0, LPC, and RTC battery. Both Type 1 and Type 2 have this common feature set and pin assignments: Type 1 has the common feature set plus: Type 2 has the common feature set plus: PC/104 PC/104 (or PC104 ) is a family of embedded computer standards which define both form factors and computer buses by the PC/104 Consortium . Its name derives from

3626-717: The PCI-104/Express and PCIe/104 buses. EPIC (Embedded Platform for Industrial Computing) is a single-board computer form factor which, like EBX, supports PC/104 peripheral boards but is smaller than EBX at 6.5 × 4.5 in (165 × 114 mm). It allows I/O connections to be implemented as either pin headers or PC-style ("real world") connectors. The standard provides specific I/O zones to implement functions such as Ethernet, serial ports, digital and analog I/O, video, wireless, and various application-specific interfaces. EPIC Express adds PCI Express expandability. In general, every PC/104 stack will contain

3700-432: The PCIe connector: CPU boards and peripherals may be designed as Type 1, Type 2, or Universal (which only uses the common subset of signals between the two types, PCIe x1 and/or USB 2.0). The Type 2 pinout was not introduced until Version 2.0 of the specification (released in 2011). PCI/104-Express products introduced prior to 2011 will be either Type 1 or Universal, but may not be explicitly labeled as such. A Type 1 bus

3774-466: The PCIe links, which allows the stack to have additional peripheral boards beyond the initial set of PCI Express links provided by CPU board. Link repopulation is not a requirement in the specification, and must be implemented on the peripheral board with a PCI Express packet switch. PCIe/104 is similar to the PCI/104-Express standard, but omits the legacy PCI bus to increase available space on

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3848-477: The PCMCIA interface is much more complex than ATA. Although most modern computers do not have physical ISA buses, almost all PCs — IA-32 , and x86-64 — have ISA buses allocated in physical address space. Some Southbridges and some CPUs themselves provide services such as temperature monitoring and voltage readings through ISA buses as ISA devices. IEEE started a standardization of the ISA bus in 1985, called

3922-578: The XT-IDE-based peripheral hard drive and memory expansion unit A590 for their Amiga 500 and 500+ computers that also supported a SCSI drive. Later models – the A600 , A1200 , and the Amiga 4000 series – use AT-IDE drives. The PCMCIA specification can be seen as a superset of ATA. The standard for PCMCIA hard disk interfaces, which included PCMCIA flash drives, allows for the mutual configuration of

3996-734: The address bits and address select signals in the ATA physical interface channel, and all operations of ATA hard disks are performed using the ATA-specified protocols through the ATA command set. The earliest versions of the ATA standard featured a few simple protocols and a basic command set comparable to the command sets of MFM and RLL controllers (which preceded ATA controllers), but the latest ATA standards have much more complex protocols and instruction sets that include optional commands and protocols providing such advanced optional-use features as sizable hidden system storage areas, password security locking, and programmable geometry translation. In

4070-575: The basic command set which became the basis of the ATA interface (and which differed greatly from the interface of IBM's fixed disk controller card for the PC XT). Direct precursors to ATA were third-party ISA hardcards that integrated a hard disk drive (HDD) and a hard disk controller (HDC) onto one card. This was at best awkward and at worst damaging to the motherboard, as ISA slots were not designed to support such heavy devices as HDDs. The next generation of Integrated Drive Electronics drives moved both

4144-423: The board (similar to the relationship between PC/104- Plus and PCI-104). The PCI Express connector location and pinout options the same as PCI/104-Express (both Type 1 and Type 2). Because the PCI bus connector is omitted, a PCIe/104 board is incompatible with PC/104- Plus and PCI-104 systems (unless a PCIe-to-PCI bridge device is used). The PC/104 Consortium's specifications cover three form factors which define

4218-438: The creation of ISA PnP , a plug-n-play system that used a combination of modifications to hardware, the system BIOS , and operating system software to automatically manage resource allocations. In reality, ISA PnP could be troublesome and did not become well-supported until the architecture was in its final days. A PnP ISA, EISA or VLB device may have a 5-byte EISA ID (3-byte manufacturer ID + 2-byte hex number) to identify

4292-479: The device. For example, CTL0044 corresponds to Creative Sound Blaster 16 / 32 PnP . PCI slots were the first physically incompatible expansion ports to directly squeeze ISA off the motherboard. At first, motherboards were largely ISA, including a few PCI slots. By the mid-1990s, the two slot types were roughly balanced, and ISA slots soon were in the minority of consumer systems. Microsoft 's PC-99 specification recommended that ISA slots be removed entirely, though

4366-574: The drive and controller to a drive bay and used a ribbon cable and a very simple interface board to connect it to an ISA slot. ATA is basically a standardization of this arrangement plus a uniform command structure for software to interface with the HDC within the drive. ATA has since been separated from the ISA bus and connected directly to the local bus, usually by integration into the chipset, for much higher clock rates and data throughput than ISA could support. ATA has clear characteristics of 16-bit ISA, such as

4440-468: The end. In late 2008, even floppy disk drives and serial ports were disappearing, and the extinction of vestigial ISA (by then the LPC bus) from chipsets was on the horizon. PCI slots are rotated compared to their ISA counterparts—PCI cards were essentially inserted upside-down, allowing ISA and PCI connectors to squeeze together on the motherboard. Only one of the two connectors can be used in each slot at

4514-568: The interference (e.g. depopulate a connector), but this may require the vendor to supply a customized version of the board. In theory, PC/104 boards are interoperable. It is possible to assemble a system using boards from several different vendors, subject to the fundamental Bus Structure compatibility issues listed above. However, compatibility issues sometimes appear. The majority of PC/104 CPU boards are x86 compatible , and are capable of running commercially available off-the-shelf PC software without modification. The standard PC I/O interfaces of

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4588-449: The mid-1990s, the ATA host controller (usually integrated into the chipset) was moved to PCI form. A further deviation between ISA and ATA is that while the ISA bus remained locked into a single standard clock rate (for backward hardware compatibility), the ATA interface offered many different speed modes, could select among them to match the maximum speed supported by the attached drives, and kept adding faster speeds with later versions of

4662-401: The next board should be set for the second slot, etc. The PCI-104 form factor includes the PCI connector, but not the PC/104 connector, in order to increase the available board real estate. Even though the PCI connector has 120 pins instead of 104, the established name was kept. The PCI connector location and pinout is identical to PC/104- Plus . Since the ISA bus is omitted, a PCI-104 board

4736-583: The original IBM AT) are likely to stick around for a while. As explained in the History section, ISA was the basis for development of the ATA interface, used for ATA (a.k.a. IDE) hard disks. Physically, ATA is essentially a simple subset of ISA, with 16 data bits, support for exactly one IRQ and one DMA channel, and 3 address bits. To this ISA subset, ATA adds two IDE address select ("chip select") lines (i.e. address decodes, effectively equivalent to address bits) and

4810-496: The port and the drive in an ATA mode. As a de facto extension, most PCMCIA flash drives additionally allow for a simple ATA mode that is enabled by pulling a single pin low, so that PCMCIA hardware and firmware are unnecessary to use them as an ATA drive connected to an ATA port. PCMCIA flash drive to ATA adapters are thus simple and inexpensive but are not guaranteed to work with any and every standard PCMCIA flash drive. Further, such adapters cannot be used as generic PCMCIA ports, as

4884-487: The same time, up to 4 devices may use one 8-bit DMA channel each, while up to 3 devices can use one 16-bit DMA channel each. Originally, the bus clock was synchronous with the CPU clock, resulting in varying bus clock frequencies among the many different IBM clones on the market (sometimes as high as 16 or 20 MHz), leading to software or electrical timing problems for certain ISA cards at bus speeds they were not designed for. Later motherboards or integrated chipsets used

4958-479: The size and shape of the board. Each form factor may utilize one of the Bus Structures listed above. The 104 Form Factor is defined to be 3.550 × 3.775 inches (90 × 96 mm), with mounting holes at all four corners of the board. The specifications also allow for a 0.5 inches (13 mm) area beyond the edge of the PCB for I/O connectors. Some PC/104 products have oversized PCBs which extended into

5032-447: The system architecture still required ISA to be present in some vestigial way internally to handle the floppy drive , serial ports , etc., which was why the software compatible LPC bus was created. ISA slots remained for a few more years, and towards the turn of the century it was common to see systems with an Accelerated Graphics Port (AGP) sitting near the central processing unit , an array of PCI slots, and one or two ISA slots near

5106-478: The system. While a handful of devices were essentially plug-n-play , this was rare. Users frequently had to configure parameters when adding a new device, such as the IRQ line, I/O address , or DMA channel. MCA had done away with this complication and PCI actually incorporated many of the ideas first explored with MCA, though it was more directly descended from EISA. This trouble with configuration eventually led to

5180-526: The top side of the board vs the bottom side. For example, a CPU board may have a Type 1 bottom PCIe connector and a Type 2 top PCIe connector. Such a CPU board would be compatible with Type 1 and/or Universal peripherals on the bottom, and compatible with Type 2 and/or Universal peripherals on the top. Similar to PC/104- Plus , a PCI/104-Express CPU boards will provide active communication on both PCI and PCIe buses. A PC/104-Express CPU board may be used with PCI-104 and PC/104- Plus peripheral modules. However,

5254-490: The two sockets into one unit. These can be found in almost every AT-class PC manufactured after the mid-1980s. The ISA slot connector is typically black (distinguishing it from the brown EISA connectors and white PCI connectors). Motherboard devices have dedicated IRQs (not present in the slots). 16-bit devices can use either PC-bus or PC/AT-bus IRQs. It is therefore possible to connect up to 6 devices that use one 8-bit IRQ each and up to 5 devices that use one 16-bit IRQ each. At

5328-477: Was a superset of the PC bus connector. In 1988, the 32-bit EISA standard was proposed by the "Gang of Nine" group of PC-compatible manufacturers that included Compaq. Compaq created the term Industry Standard Architecture (ISA) to replace PC compatible . In the process, they retroactively renamed the AT bus to ISA to avoid infringing IBM's trademark on its PC and PC/AT systems (and to avoid giving their major competitor, IBM, free advertisement). IBM designed

5402-545: Was introduced with the IBM PC/AT . This bus was officially termed I/O Channel by IBM. It extends the XT-bus by adding a second shorter edge connector in-line with the eight-bit XT-bus connector, which is unchanged, retaining compatibility with most 8-bit cards. The second connector adds four additional address lines for a total of 24, and 8 additional data lines for a total of 16. It also adds new interrupt lines connected to

5476-494: Was limited to 128 KiB sections, leading to problems when mixing 8- and 16-bit cards as they could not co-exist in the same 128 KiB area. This is because the MEMCS16 line is required to be set based on the value of LA17-23 only. ISA is still used today for specialized industrial purposes. In 2008, IEI Technologies released a modern motherboard for Intel Core 2 Duo processors which, in addition to other special I/O features,

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