This is inside PC world called second PC bus generation, because ISA is considered first generation. Usualy bus is designed to last for 10-15 years which ISA accomplished. Intel made big mistake with VLB bus, it was orientated to one type of mircoProcessors, so they suggested universal solution that is connected to intern bus over microProcessor with Host Bridge, which is actually adjusting unit. That means that bus is phisicaly and logicaly and electricaly separated from microProcessor, so type of microProcessor doesn't jeopardise bus. Standard was promoved in 1992 and held until today, even if has been extended. Standard PCI bus is 32-bit and runs on 33,3 MHz nad is present at 99,9% PC MotherBoards (MB). Besides, there are numberous variants that work on 66, 100 and 133 MHz, like 64-bit version of PCI, but this soulutions are used ostly on server computers and graphics work stations.




PCI bus brins much better performanses according to VLB bus, beforeall thanks to specific improvements like:
- Burst Mode, possibility of data transmition into burst mode, which presents block transfer of data array
- Bus Mastering, possibility of PCI device to take control over bus and to make data transmission direct. This is first bus that popularised Bus Mastering, before O.S. and applications could use that advantage.
PCI bus allows same time bus mastering of more devices, with kind of work that non device on bus can block other device.
- High bandwidth PCI 2.1 specification (64-bit), which works on 66 MHz, makes first standards bandwidth 4 times larger. But this specification is mostly used on professional systems, on this specification AGP was based.

With grow of bus frequency, problem of signal synhronization on bus becomes complex. Extendion of work frequency is negatively reflect on signal wave form on bus and advent of late because capacitive character comes to expression of bus load and nus-capacity of semiconductor units. PCI bus allows up to 10 standard capcacity duty loads, 5 plugged modules into PCI slots (1 PCI modul treat as 2 capacity duty loads).

With bus development, specific graphics cards appeared on marked, so today we can find:

PCI graphics cards
AGP graphics cards
PCI-E graphics cards

PCI graphics cards, today are very little in use, 'cause of relatively weak bandwidth of PCI bus, but they used very good, and may be still in use for users that use only office application, and other graphicaly low-requirement softwares. But, with appearence of "realistic" 3D games, which made first 3D objects, not 2D pictures,hardware acceleration was invented, which means 3D rendering directly through hardware not with software emulation. First cards, then called 3D accelerators, PCI bus was just about enough. When new tecnologies were found, and with speed acceleration, there was need for faster bus. Therefore AGP was developed

AGP cards usualy posses hardware acceleration, and also larger amounts of memory then PCI graphics cards, and with that, they are faster. AGP graphics cards today have bigger part of market, but AGP bus is reached its maximum, like other buses that use parallel datatransmission. Therefore it is expected that PCI Express bus, that is serial, in near future stoppes being primary and only, so AGP graphics cards today are eaven not produced, they started making only PCI-E versions.