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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.


Click here to see how to identify which card fits in which slot.

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). CPUís and RAM use their own (and different) connections. The labeled slots are explained below:

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 CPUís and all those previous will not have this slot. All current motherboards will have one of these slots if there isnít 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. Donít 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 computerís 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 ĎLegacy devicesí. This means that it does not use Plug ín Play to allocate resources needed to communicate with system. Without Plug Ďn Play, the user must set I/O addresses and IRQís 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.

Geek Section

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.