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What is the difference between System bus and PCI bus. How can I find the difference between the both. what is the main differences. I want to make some project work on the PCI bus working. So I am not able to find out this actual usage and difference among the same. Also what is VESA stands for and on what it is implemented the same.
System Bus vs. PCI Bus, twenty or 30 years ago, the processors were so slow that the processor and the bus were corresponding. The bus ran at the similar or identical speed as the processor, and there was one bus in the machine. Today, the processors run so fast that a good number of computers have two or more buses. Each bus concentrates in a certain type of traffic.
A representative desktop PC today has two most important buses: The first one, known as the system bus or local bus, attach the microprocessor (central processing unit) and the system memory. This is the fastest bus in the system and the second one is a slower bus for exchange a few words with things like hard disks and sound cards.
One very universal bus of this category is known as the PCI bus. These slower buses attach to the system bus through a bridge, which is a part of the computer's chipset and acts as a traffic cop, incorporating the data from the other buses to the system bus. Theoretically there are other buses as well. For example, the Universal Serial Bus (USB) is a way of connecting things like cameras, scanners and printers to your computer. It uses a thin wire to attach to the devices, and many devices can share that wire concurrently. Fire wire is another bus, used today typically for video cameras and external hard drives.
The cool thing regarding VL-Bus (named after VESA, the Video Electronics Standards Association, which twisted the standard) is that it was 32 bits wide and operated at the speed of the local bus, which was generally the speed of the processor itself. The VL-Bus fundamentally tied directly into the CPU. This worked okay for a single device, or maybe even two. But connecting extra than two devices to the VL-Bus introduced the possibility of interference with the presentation of the CPU. Because of this, the VL-Bus was characteristically used only for connecting a graphics card, a component that really benefits from high-speed access to the CPU.
During the early 1990s, Intel established a new bus standard for contemplation, the Peripheral Component Interconnect (PCI) bus. PCI presents a hybrid of sorts between ISA and VL-Bus. It presents direct access to system memory for associated devices, but uses a bridge to attach to the front side bus and therefore to the CPU. Fundamentally, this means that it is capable of even higher presentation than VL-Bus while eliminating the potential for interference with the CPU.