Fungsi Isa Slots

Bus ISA (Industry Standard Architecture) adalah sebuah arsitektur bus dengan bus data selebar 8-bit yang diperkenalkan dalam IBM PC 5150 pada tanggal 12 Agustus 1981.Bus ISA diperbarui dengan menambahkan bus data selebar menjadi 16-bit pada IBM PC/AT pada tahun 1984, sehingga jenis bus ISA yang beredar pun terbagi menjadi dua bagian, yakni ISA 16-bit dan ISA 8-bit. Slot ekspansi tertua yang disebut Slot ISA adalah slot ekspansi 8-bit memiliki kecepatan transfer 4.77 Mbyte/detik atau8.33 Mbyte/detik. Meskipun kecepatani transfer rate yang rendah, ISA mencukupi kebutuhan saat itu, karena bus-bus I/O semacam serial port, parallel port,kontrolir floppy disk, kontrolir keyboard dan lainnya juga memiliki kecepatan yang rendah. ISA atau (Industry Standard Architecture) yiatu slot standar VGA Card sekitar akhir tahun 1980-an. Slot jenis ini saat ini sudah tidak dipakai lagi pada motherboard jenis baru. VGA Card jenis ISA ini bisa mengirimkan data 2 sampai 3 MB per detik (Megabytes per sekon).

ISA (Industry Standard Architecture) ISA merupakan standar slot VGA Card yang diperkenalkan pada akhir tahun 80-an. Hanya saja slot VGA jenis ini sudah tidak lagi digunakan pada Motherboard, bahkan sudah menghilang dari pasaran. ISA sendiri konon mampu mentransfer data dengan kecepatan 2-3mbps. PCI (Peripheral Component Interconnect). Komputer lama menggunakan slot ISA, yang merupakan bus yang lamban. Sejak kemunculan-nya sekitar tahun 1992, bus PCI masih digunakan sampai sekarang, hingga keluar versi terbarunya yaitu PCI Express (add-on). ISA (International Standard Architecture) adalah sebuah arsitektur bus dengan bus data selebar 8-bit yang diperkenalkan dalam IBM PC 5150.

Enhanced Industry Standard Architecture
Year created1988; 32 years ago
Created byGang of Nine
Superseded byPCI (1993)
Width in bits32
No. of devices1 per slot
Speed8.33 MHz
Half-duplex 33 MB/s[1]
Hotplugging interfaceNo
External interfaceNo
SCSI controller (Adaptec AHA-1740)
Fast SCSI RAID controller (DPT PM2022)
ELSA Winner 1000 Video card for ISA and EISA

The Extended Industry Standard Architecture (in practice almost always shortened to EISA and frequently pronounced 'eee-suh') is a bus standard for IBM PC compatiblecomputers. It was announced in September 1988 by a consortium of PC clone vendors (the Gang of Nine) as a counter to IBM's use of its proprietaryMicro Channel architecture (MCA) in its PS/2 series.[2]

In comparison with the AT bus, which the Gang of Nine retroactively renamed to the ISA bus to avoid infringing IBM's trademark on its PC/AT computer, EISA is extended to 32 bits and allows more than one CPU to share the bus. The bus mastering support is also enhanced to provide access to 4 GB of memory. Unlike MCA, EISA can accept older XT and ISA boards — the lines and slots for EISA are a superset of ISA.

EISA was much favoured by manufacturers due to the proprietary nature of MCA, and even IBM produced some machines supporting it. It was somewhat expensive to implement (though not as much as MCA), so it never became particularly popular in desktop PCs. However, it was reasonably successful in the server market,[3] as it was better suited to bandwidth-intensive tasks (such as disk access and networking). Most EISA cards produced were either SCSI or network cards. EISA was also available on some non-IBM-compatible machines such as the AlphaServer, HP 9000-D, SGI Indigo2 and MIPS Magnum.

By the time there was a strong market need for a bus of these speeds and capabilities for desktop computers, the VESA Local Bus and later PCI filled this niche, and EISA vanished into obscurity.



The original IBM PC included five 8-bit slots, running at the system clock speed of 4.77 MHz. The PC/AT, introduced in 1984, had three 8-bit slots and five 16-bit slots, all running at the system clock speed of 6 MHz in the earlier models and 8 MHz in the last version of the computer. The 16-bit slots were a superset of the 8-bit configuration, so most 8-bit cards were able to plug into a 16-bit slot (some cards used a 'skirt' design that physically interfered with the extended portion of the slot) and continue to run in 8-bit mode. One of the key reasons for the success of the IBM PC (and the PC clones that followed it) was the active ecosystem of third-party expansion cards available for the machines. IBM was restricted from patenting the bus and widely published the bus specifications.

As the PC-clone industry continued to build momentum in the mid- to late-1980s, several problems with the bus began to be apparent. First, because the 'AT slot' (as it was known at the time) was not managed by any central standards group, there was nothing to prevent a manufacturer from 'pushing' the standard. One of the most common issues was that as PC clones became more common, PC manufacturers began increasing the processor speed to maintain a competitive advantage. Unfortunately, because the ISA bus was originally locked to the processor clock, this meant that some 286 machines had ISA buses that ran at 10, 12, or even 16 MHz. In fact, the first system to clock the ISA bus at 8 MHz was the turbo 8088 clones that clocked the processors at 8 MHz. This caused many issues with incompatibility, where a true IBM-compatible third-party card (designed for an 8 MHz or 4.77 MHz bus) might not work in a higher-speed system (or even worse, would work unreliably). Most PC makers eventually decoupled the slot clock from the system clock, but there was still no standards body to 'police' the industry.

As companies like Dell modified the AT bus design,[4] the architecture was so well entrenched that no single clone manufacturer had the leverage to create a standardized alternative, and there was no compelling reason for them to cooperate on a new standard. Citrix workspace download mac catalina. Because of this, when the first 386-based system (the Compaq Deskpro 386) hit the market in 1986, it still supported 16-bit slots. Other 386 PCs followed suit, and the AT (later ISA) bus remained a part of most systems even into the late 1990s.

Meanwhile, IBM began to worry that it was losing control of the industry it had created. In 1987, IBM released the PS/2 line of computers, which included the MCA bus. MCA included numerous enhancements over the 16-bit AT bus, including bus mastering, burst mode, software-configurable resources, and 32-bit capabilities. However, in an effort to reassert its dominant role, IBM patented the bus and placed stringent licensing and royalty policies on its use. A few manufacturers did produce licensed MCA machines (most notably, NCR), but overall the industry balked at IBM's restrictions.

Steve Gibson proposed that clone makers adopt NuBus.[5] Instead, a group (the 'Gang of Nine'), led by Compaq, created a new bus, which was named the Extended (or Enhanced) Industry Standard Architecture, or 'EISA' (and the 16-bit bus became known as Industry Standard Architecture, or 'ISA').[6] This provided virtually all of the technical advantages of MCA, while remaining compatible with existing 8-bit and 16-bit cards, and (most enticing to system and card makers) minimal licensing cost.

The EISA bus slot is a two-level staggered pin system, with the upper part of the slot corresponding to the standard ISA bus pin layout. The additional features of the EISA bus are implemented on the lower part of the slot connector, using thin traces inserted into the insulating gap of the upper / ISA card card edge connector. Additionally, the lower part of the bus has five keying notches, so an ISA card with unusually long traces cannot accidentally extend down into the lower part of the slot.

Fungsi Isa Slots

Intel introduced their first EISA chipset (and also their first chipset in the modern sense of the word) as the 82350 in September 1989.[7][8] Intel introduced a lower-cost variant as the 82350DT, announced in April 1991; it began shipping in June of that year.[9]

The first EISA computer announced was the HP Vectra 486 in October 1989.[10] The first EISA computers to hit the market were the Compaq Deskpro 486 and the SystemPro.[citation needed] The SystemPro, being one of the first PC-style systems designed as a network server, was built from the ground up to take full advantage of the EISA bus. It included such features as multiprocessing, hardware RAID, and bus-mastering network cards.

One of the benefits to come out of the EISA standard was a final codification of the standard to which ISA slots and cards should be held (in particular, clock speed was fixed at an industry standard of 8.33 MHz). Thus, even systems that didn't use the EISA bus gained the advantage of having the ISA standardized, which contributed to its longevity.

The 'Gang of Nine'[edit]

The Gang of Nine was the informal name given to the consortium of personal computer manufacturing companies that together created the EISA bus. Rival members generally acknowledged Compaq's leadership, with one stating in 1989 that within the Gang of Nine 'when you have 10 people sit down before a table to write a letter to the president, someone has to write the letter. Compaq is sitting down at the typewriter'.[6] The members were:[2]

Technical data[edit]

bus width32 bits
compatible with8-bit ISA, 16-bit ISA, 32-bit EISA
pins98 + 100 inlay
Vcc+5 V, −5 V, +12 V, −12 V
clock8.33 MHz
theoretical data rate (32-bit)about 33 MB/s (8.33 MHz × 4 bytes)
usable data rate (32-bit)about 20 MB/s

Although the MCA bus had a slight performance advantage over EISA (bus speed of 10 MHz, compared to 8.33 MHz), EISA contained almost all of the technological benefits that MCA boasted, including bus mastering, burst mode, software-configurable resources, and 32-bit data/address buses. These brought EISA nearly to par with MCA from a performance standpoint, and EISA easily defeated MCA in industry support.

EISA replaced the tedious jumper configuration common with ISA cards with software-based configuration. Every EISA system shipped with an EISA configuration utility; this was usually a slightly customized version of the standard utilities written by the EISA chipset makers. The user would boot into this utility, either from floppy disk or on a dedicated hard-drive partition. The utility software would detect all EISA cards in the system and could configure any hardware resources (interrupts, memory ports, etc.) on any EISA card (each EISA card would include a disk with information that described the available options on the card) or on the EISA system motherboard. The user could also enter information about ISA cards in the system, allowing the utility to automatically reconfigure EISA cards to avoid resource conflicts.

Similarly, Windows 95, with its Plug-and-Play capability, was not able to change the configuration of EISA cards, but it could detect the cards, read their configuration, and reconfigure Plug-and-Play hardware to avoid resource conflicts. Windows 95 would also automatically attempt to install appropriate drivers for detected EISA cards.

Industry acceptance[edit]

EISA's success was far from guaranteed. Many manufacturers, including those in the 'Gang of Nine', researched the possibility of using MCA. For example, Compaq actually produced prototype DeskPro systems using the bus. However, these were never put into production, and when it was clear that MCA had lost, Compaq allowed its MCA license to expire (the license actually cost relatively little; the primary costs associated with MCA, and at which the industry revolted, were royalties to be paid per system shipped).

On the other hand, when it became clear to IBM that Micro Channel was dying, IBM licensed EISA for use in a few server systems.

See also[edit]

  • Industry Standard Architecture (ISA)
  • Micro Channel architecture (MCA)
  • VESA Local Bus (VESA)
  • Peripheral Component Interconnect (PCI)
  • Accelerated Graphics Port (AGP)
  • PCI Express (PCIe)
  • Low Pin Count (LPC)


  1. ^Mueller, Scott (2003). Upgrading and Repairing PCS. Que Publishing. p. 310. ISBN9780789729743. ISA bus speed.
  2. ^ abCompaq Leads 'Gang of Nine' In Offering Alternative to MCA, InfoWorld, Sep 19, 1988.
  3. ^Sean K. Daily (1998). Optimizing Windows NT. Wiley. p. 137. ISBN978-0-7645-3110-1. EISA is still found on many of today's modern servers[,] owing to its long-standing presence in the PC server market.
  4. ^Lewis, Peter H. (1988-04-24). 'Introducing the First PS/2 Clones'. The New York Times. Retrieved 6 January 2015.
  5. ^Lemmons, Phil (August 1987). 'Editorial'. BYTE. p. 6. Retrieved 6 November 2013.
  6. ^ abLaPlante, Alice; Furger, Roberta (1989-01-23). 'Compaq Vying To Become the IBM of the '90s'. InfoWorld. pp. 1, 8. Retrieved 17 March 2016.
  7. ^Scott M. Mueller (2011). Upgrading and Repairing PCs (20th ed.). Que Publishing. p. 24. ISBN978-0-13-268218-3.
  8. ^Ziff Davis, Inc. (26 September 1989). 'First EISA chips delivered'. PC Magazine: The Independent Guide to IBM-Standard Personal Computing. PC Magazine: 65. ISSN0888-8507.
  9. ^Louise Fickel (29 April 1991). 'Intel Debuts EISA Chip Set for Lower Cost 32-Bit Systems'. InfoWorld : The Newspaper for the Microcomputing Community. InfoWorld: 27. ISSN0199-6649.
  10. ^

External links[edit]

Retrieved from ''

Alternatively known as a bus slot or expansion port, an expansion slot is a connection or port inside a computer on the motherboard or riser card. It provides an installation point for a hardware expansion card to be connected. For example, if you wanted to install a new video card in the computer, you'd purchase a video expansion card and install that card into the compatible expansion slot.

Computer expansion slots

Below is a listing of expansion slots commonly found in a computer and the devices associated with those slots. Clicking on any of the links below provide you with additional details.

  • AGP - Video card.
  • AMR - Modem, sound card.
  • CNR - Modem, network card, sound card.
  • EISA - SCSI, network card, video card.
  • ISA - Network card, sound card, video card.
  • PCI - Network card, SCSI, sound card, video card.
  • PCI Express - Video card, modem, sound card, network card.
  • VESA - Video card.

Many of the above expansion card slots are obsolete. You're most likely only going to encounter AGP, PCI, and PCI Express when working with computers today. In the picture below is an example of what expansion slots may look like on a motherboard. In this picture, there are three different types of expansion slots: PCI Express, PCI, and AGP.

How many expansion slots does my computer have?

Every computer motherboard is different, to determine how many expansion slots are on your computer motherboard identify the manufacturer and model of the motherboard. Once you've identified the model of motherboard, you can find complete information about the motherboard in its manual.

Adding additional expansion slots for older motherboards could be accomplished by using a riser board, which would add several ISA or PCI slots. Today, riser boards are rarely used with motherboards, as there is limited need for additional expansion slots with modern motherboards.

What type of expansion slots are on my motherboard?

As mentioned above, every motherboard model is unique, so to determine the type of expansion slots on the motherboard, consult the board's specifications and owner's manual. You can also open the computer case and visually examine the motherboard.

Why do computers have expansion slots?

Computers have expansion slots to give the user the ability to add new devices to their computer. For example, a computer gamer may upgrade their video card to get better performance in their games. An expansion slot allows them to remove the old video card and add a new video card without replacing the motherboard.

What is the most common expansion slot today?

Fungsi Isa Slots Free

Today, the most commonly used expansion slot used and found on computer motherboards is the PCI Express expansion slot.

Does a laptop have an expansion slot?

Laptops do not have expansion slots like a desktop computer. However, some laptops do have PC Cards that can be inserted into the side of the laptop. They may also have a Cardbus slot for an ExpressCard to be added.

Fungsi Isa Slot

Related expansion slot pages

Fungsi Isa Slots Download

Expansion, Expansion card, Motherboard terms, Seated