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Recognizing interfaces, connectors and connections (2/2)

Guide written by Falkra, whom I would like to thank once again for all her work on The second part of this visual guide, this time dedicated to the connectors and connections inside the machine. (>>>Part One)

To see the section on interfaces outside the PC, go to this page

Internal USB

Internal USB ports are often found on motherboards, shown here in blue. On the right, the type of plug, which leads to a USB socket on the front or rear of the case.


Sata interface : Two connectors on the motherboard side (left photo), then on the hard disk side (right photo): on the left, the larger disk power supply, and on the right, the data connection.

The two cables needed for the hard disk: on the left, the data cable; on the right, the power cable.

Caution: fragile connector.

Developed name: Serial ATA

Other names: without

Typical connection: hard disks, some optical drives (burners).

An e-Sata standard exists for the external variant of this interface.

IDE An interface using ATA/ATAPI protocols. The latest hard drives use the ATA7 version (ultra DMA 6, ultra DMA 133).

Motherboard side (black and blue), then cable.

Here, on the left, 4 IDE ports, and on the right, the narrower floppy drive port.

Cables (or cables). The photo on the right shows the two types of cables, with 40 and 80 wires. For more recent peripherals, 80-wire cables are the only ones that can be used for ATA100 and ATA133 hardware (UDMA 5 and 6). Below that, 40 wires are sufficient.

Developed name: Integrated Drive Electronics.

Other names: parallel ATA, PATA.

Conventional connection: hard disks, optical drives. Replaced by serial ATA for hard disks.


The interface for graphics cards and other peripherals, an evolution of the PCi bus. From top to bottom, 4x, 16x and 1x versions.

PCi express 16x graphics card and connector:

Developed name: Peripheral Component Interconnect Express.

Other names: PCIE.

Classic connection: expansion cards, especially graphics cards.

AGP The bus for graphics cards, superseded by PCI Express 16x (there will be no AGP16x). It has had several variants, differing in voltage and speed:

Here are the AGP bus standards:

AGP 1.0: 3.3 V - 1x, 2x

AGP 2.0: 1.5 V - 1x, 2x, 4x

AGP 2.0 universal: 1.5 V, 3.3 V - 1x, 2x, 4x

AGP 3.0 (latest): 1.5 V - 4x, 8x

Here it is on the motherboard side, brown by default, sometimes red or burgundy:

A 1.5-volt AGP with the ejector mechanism:

This is a 3.3 volt AGP:

And the graphics card connector (3.3 volts):

A graphics card compatible with 1.5 and 3.3 volts :

Name developed: Advanced Graphic Port.

Other names: without

Connection: graphics card. PCI

An interface for expansion cards of all kinds. Still present, but less and less used, due to the integration of hardware on motherboards or the existence of comparable products in the form of USB peripherals.

Expansion card connector :

A PCI-X slot, an evolution of the classic PCi bus (increased bandwidth). Found in professional machines:

Developed name: Peripheral Component Interconnect.

Other names: without

Classic connection: extension boards. RAM slots Designed to accommodate RAM, these connectors feature a coding pin whose location changes according to the type of memory (SDram, DDR, etc.).

Here for SDRam

Here for RAM DDR

The two colors indicate the slots that need to be filled with modules of the same type and capacity to benefit from Dual Channel technology.

Other names: memory bank.

Connection: RAM. Power supply side The type of plug is called "molex", after the group that produces them. But this only designates the way the contact is made, via a plastic connector containing the pins. There are 4*1 molex plugs (those supplying optical units, for example).

On the left, the classic socket for optical drives and non-Sata hard disks.

On the right, the socket for floppy disk drives.

The connector on the left is an additional, obsolete auxiliary power supply. On the other hand, the right connector (2x2) often completes the processor power supply.

On the left, the classic ATX socket that powers the motherboard, on the power supply side, on the right, on the motherboard side.

On some power supplies, the ATX socket may have a built-in 2x2-pin module.

There will be 28 instead of the usual 24 pins.

Name developed: Molex 8981-4P (classic 4x1 plug).

Other names: without

Classic connection: power supply...

Molex 4x1: hard disks, optical drives, some graphics cards. Fan sockets On the right, the 3-pin motherboard connector used by 8 cm fans and below. Beyond that, fans use a classic 4x1 molex plug. When there are 3 wires, the 3ᵉ is used to count the fan's revolutions per minute.

This connector is often white.

Developed name: 3-pin fan plug...

Other names: ...

Classic connection: fans, with or without rpm counter.

ISA An obsolete interface no longer in use. These are the pre-PCi expansion slots. In the photo below, they are black, on the right.

The one below is an 8-bit ISA, the others are 16-bit.

The connector of an expansion card :

The ISA data bus is 16-bit (8-bit for the previous, shorter version), unlike PCi, which is 32-bit.

Developed name: Industry Standard Architecture.

Other names: without

Classic connection: extension cards. Discontinued.

Part One Connections, outside and around the PC, go to this page

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