Different Expansion Slots

• Expansion Slots Agp
• Explain About Different Expansion Slots On Motherboard

After knowing the expansion slots definition, this section is going to talk about the different types of expansion slots. Over the years, you can find these expansion slots: PCI, AGP, AMR, CNR, ISA, EISA, and VESA, but the most popular expansion slot today is PCIe. Generally, PCI Express refers to the actual expansion slots on the motherboard that accept PCIe-based expansion cards and to the types of expansion cards themselves. PCI Express has all but replaced AGP and PCI, both of which replaced the oldest widely-used connection type called ISA. ISA: The most ancient type of expansion slot is the ISA, which stands for (get this) Industry Standard Architecture. That’s because it never really had a name until another, better type of expansion slot came along. ISA slots hang around to be compatible with older expansion cards.

PC Card Slot Types

• ISA
• AGP
• PCI
• PCI-X
• PCI-E (PCIexpress)

ISA

ISA, or Industry Standard Architecture, is an 8bit or 16bit parallel bus system that allowed up to 6 devices to be connected to a PC. Virtually all IBM-compatible PCs made before the Pentium were based on the ISA (IBM's PC AT) bus. This asynchronous bus architecture uses 16-bit addresses and an 8-MHz clock and handles a maximum data throughput of 2 MB/s to 3 MB/s.

ISA is the precursor to PCI. Standing for 'Industry Standard Architecture' It was common from the early 1980s to the mid 1990s. ISA was a typically inelegant solution for the time, and required one to know exactly what one was doing- PnP was rare, even for so called 'ISA PnP' peripherals. In the end, the combination of flexibility, ease of use, and greater capability allowed PCI to supersede ISA.

PCI

The PCI bus architecture is a processor-independent bus specification that allows peripherals to access system memory directly without using the CPU. Not only does this free up the CPU to service other application calls, but PCI users also can simultaneously acquire data to memory and analyze existing data in real time, all while communicating with other functions on the network.

More importantly, PCI peripherals running asynchronously can send data along the 32-bit bus at a rate of up to 132 MB/s or 66 MS/s.

AGP

The Accelerates Graphics Port is a high-speed point-to-point channel for attaching a video card to a computer's motherboard. It was created in 1997 yet by 2004 was largely replaced by PCI Express. The primary advantage of AGP over PCI is that it provides a dedicated pathway between the slot and the processor rather than sharing the PCI bus. In addition to a lack of contention for the bus, the point-to-point connection allows for higher clock speeds. AGP also uses sideband addressing, meaning that the address and data buses are separated so the entire packet does not need to be read to get addressing information. This is done by adding eight extra 8-bit buses which allow the graphics controller to issue new AGP requests and commands at the same time with other AGP data flowing via the main 32 address/data (AD) lines. This results in improved overall AGP data throughput.

PCI-X

PCI-X stands for 'PCI-eXtended'. PCI-X is a computer bus and expansion card standard that enhances the 32-bit PCI Local Bus for higher bandwidth demanded by servers. It is a double-wide version of PCI, running at up to four times the clock speed, but is otherwise similar in electrical implementation and uses the same protocol.[1] It has itself been replaced in modern designs by the similar-sounding PCI Express, which features a very different logical design, most notably being a 'narrow but fast' serial connection instead of a 'wide but slow' parallel connection.

PCI-X revised the conventional PCI standard by doubling the maximum clock speed (from 66 MHz to 133 MHz)[1] and hence the amount of data exchanged between the computer processor and peripherals. Conventional PCI supports up to 64 bits at 66 MHz (though anything above 32 bits at 33 MHz is only seen in high-end systems) and additional bus standards move 32 bits at 66 MHz or 64 bits at 33 MHz. The theoretical maximum amount of data exchanged between the processor and peripherals with PCI-X is 1.06 GB/s, compared to 133 MB/s with standard PCI. PCI-X also improves the fault tolerance of PCI allowing, for example, faulty cards to be reinitialized or taken offline.

PCI Express

PCIe, or Peripheral Component Interconnect Express, is a computer expansion card standard designed to replace the older PCI, PCI-X, and AGP standards. PCI Express is used in consumer, server, and industrial applications, as a motherboard-level interconnect (to link motherboard-mounted peripherals) and as an expansion card interface for add-in boards. A key difference between PCIe and earlier buses is a topology based on point-to-point serial links, rather than a shared parallel bus architecture.

Bandwidth

Below is a table showing the different buses/card slot types and their maximum bandwidths:

* Note - Since PCI Express is a serial based technology, data can be sent over the bus in two directions at once. Normal PCI is Parallel, and as such all data goes in one direction around the loop.

Identifying Expansion Slots
ISA vs. PCI vs. AGP

First thing to know is these things are going to be found inside your computer's case. Which means to see them or install something in them you will need to remove the cover from your case. When you open your case, you will see under all the rest of the stuff what is called the motherboard (or mainboard). Below is a picture of what a motherboard may look like. Keep in mind, yours will probably not look like this, but it should look similar.

The three types of slots labeled are the expansion slots, any card that is to be installed will fit into one of these three types of slots (except for a very few proprietary cards). CPU’s and RAM use their own (and different) connections. The labeled slots are explained below:

Expansion Slots Agp

AGP - Advanced Graphics Port; This slot will be located closest to the CPU and farthest from the ISA slots if there are any. The connector will be brown in color and be further from the back of the computer than the other types of slots (PCI and ISA). Not on all motherboards will have an AGP slot, some motherboards that support Pentium MMX and AMD K6-2 CPU’s and all those previous will not have this slot. All current motherboards will have one of these slots if there isn’t integrated video. The only thing that can be put in this slot are video cards. No motherboard can have more than 1 (one) of these (for an explanation as to why see the geek section below). Not all video cards will fit into this slot. You will need to determine if your video card is made for AGP or not. The slot runs at 66 Mhz with specifications for 1x, 2x and 4x multipliers of the 66 Mhz. Some newer video cards are only 2x/4x compatible and will not work in motherboards that are only 1x compatible. If your motherboard manual mentions nothing of 2x or 4x then it was probably made before 2x and 4x specifications came out.

PCI - Some motherboards can have upto 7 of these slots. The connectors for these slots are white in color. Almost any type of card can be found to work in one of these slots, (Video cards, Network, Modems, SCSI, and more). Some 486 computers may have these slots, and all systems since then will have these slots, except certain proprietary systems. If there are ISA slots on your board, then the PCI slot and the ISA slot next to each other are known as a 'shared' slot. This means that only one of these two can be used. Don’t worry about trying to remember this as the two slots will try to use the same back plate of the case and make it impossible to put both cards in at the same time. The bus runs at 33 Mhz which is shared between all of the PCI cards. So a card only gets the full 33 Mhz bus speed if no other PCI cards are in use.

ISA - These are the original slot used to expand your computer’s function. The connectors are black in color and longer than the others. Some of the devices that fit in these slots are referred to as ‘Legacy devices’. This means that it does not use Plug ’n Play to allocate resources needed to communicate with system. Without Plug ‘n Play, the user must set I/O addresses and IRQ’s using jumpers or software. These slots run at 8 Mhz.

General Note: The information provided here is for mainstream and generic/non-proprietary systems. Certain proprietary systems stray away from the standards and cannot be expected to be covered here.

Explain About Different Expansion Slots On Motherboard

Port vs. Bus - Devices and connections that are called ports have only 1 connection. They are designed to talk to one device on the other end of the connection. There is nothing in the protocol to say which device the command or data being sent or requested is for. If something is sent it is only expecting a response from the one device on the other end. On the otherhand, a bus is designed to handle more than one device. In its design and protocols there are specifications for identifying which device attached to the bus is to be interpreting what is sent.