Situatie
Peripheral Component Interface – express (PCIe) is a bus that allows expansion cards inside your computer to communicate with other components. You use the PCIe system by putting cards into slots on the motherboard. These cards can be things like graphics cards, RAID cards, network cards, even co-processors.
Expansion cards can communicate with other system resources by using lanes Lanes are represented by an “x” followed by the number of lanes being used. Multiple lanes can be used by one card, and we call these configurations “modes”. The PCIe 3.0 specification allows for these modes and slots, in ascending order by bandwidth/length:
x1
x2
x4
x8
x16
x32 (for all intents and purposes this doesn’t actually exist).
When a card is placed into a slot and the computer booted up, the system negotiates with the card to determine which mode to operate in. If there is only one card in the system, and it is in a slot that supports it’s maximum mode, then the system will give it that mode, otherwise it will give it the maximum mode supported by the slot. For example: If a x16 card is in a x16 slot, then it will run in x16 mode. If, however, you place a x8 card in a x16 slot, then it will still run in x8 mode.
When multiple cards are used, things get a little more complicated, but it is eased by the fact that all cards can operate in any mode below their listed mode. Processors and motherboards each have a maximum number of lanes that they will support.
A PCIe lane is simply one channel of serial communication. The supported lane configurations are 1, 2, 4, 8, 16, and 32 (for all intents and purposes this doesn’t exist). Each configuration has it’s own slot. You can differentiate them by length, a 1 lane slot is the shortest while a 32 lane slot is the longest. There are also PCIe modes. A mode is simply how many lanes a card is actually using. It is independent from how many lanes are available to the card. Any card or slot may operate in any mode below it’s maximum mode, but must be in a slot that is the same physical size. Lanes and modes are denoted by an “x” preceding the number of lanes. For example: x1, x2, x4, x8, x16, or x32.
You can think of each lane like a two lane road (one lane in each direction). If we only have x1 lanes then we have a two lane road. If we have x2 lanes then we have a 4 lane highway. With x4 we have an 8 lane freeway. With x8 we have a 16 lane superhighway.
Leave A Comment?