Ever since graphic cards became popular, motherboard and graphic card manufacturers worked hand in hand to produce the best throughput possibilities. Through the years, new buses were produced by motherboard manufacturers to support the unconventionally immense throughput demands of modern applications of the day and age.
The PCI bus was not originally intended for graphic cards. It was originally intended as a 32-bit universal bus for devices to replace the original 16-bit and 8-bit Industry Standard Architecture (ISA) bus of the past. Graphic cards have sought this new 32-bit bus as a foundation for their architecture. The idea became a success at first. After a while, it did not suffice. A new slot had to be designed to keep up with demands.
The Accelerated Graphics Port (AGP) is the first dedicated channel for graphic cards ever produced. It was introduced in 1997 by Intel in its i440LX Slot 1 chipset. The main advantage that AGP has over PCI is that it runs a dedicated connection from the channel to the CPU. PCI graphic cards would have to share the bus with the other devices attached to each channel. PCI was still used, however, for people who wanted multiple display capabilities. Ever since AGP was produced, it has undergone many improvements, and each new version is backwards compatible with its previous versions.
PCI Express x16
Although PCI Express (PCIe) was meant to be a universal bus, the 16-lane slots on motherboards became favorable for extremely fast graphic cards. Card manufacturers immediately began producing cards that ran with the PCIe bus. It shortly became an incredible success, more so than PCI or AGP.
PCIe and PCI
PCIe is interesting because it can be recognized in systems that can only recognize PCI or AGP buses. Unlike the original PCI bus, devices connected to the PCIe bus do not need to share the bus with each other. You can enjoy the full potential of each device you connect to any PCIe slot without compromising speed with a shared bus. This is also known as a serial bus, and the idea is a reflection of other concepts, such as USB (cleverly named the Universal Serial Bus and created as a replacement of the old serial COM ports of computers).
PCIe and AGP
After PCIe was released, AGP quickly lost its place as an innovative means of graphic acceleration because most motherboards contained only one AGP slot. However, some motherboards would implement even up to three PCIe slots. It is also obviously better to have the system rely on only one universal bus, much like how PCI was intended. AGP is only able to reach barely three quarters of the fastest speed that PCIe can deliver.
- Photo Credit David Henry:Wikimedia Commons
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