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The PCI bus was adequate for many years, providing enough bandwidth for all the peripherals most users might want to connect. All except one: graphics cards. In the mid 1990s, graphics cards were getting more and more powerful, and 3D games were demanding higher performance. The answer; Intel developed the Accelerated Graphics Port (AGP).

AGP is a bus dedicated completely to graphics cards. The bandwidth across the AGP bus isn't shared with any other components. Although PCI continues to be the bus of choice for most peripherals, AGP has taken over the specialized task of graphics processing. However, a new bus technology is about to hit the market that just might spell the end for AGP

Interrupt requests (IRQ) - An IRQ, also known as a hardware interrupt, is used by the various parts of a computer to get the attention of the CPU. For example, the mouse sends an IRQ every time it is moved to let the CPU know that it's doing something. Before PCI, every hardware component needed a separate IRQ setting. But PCI manages hardware interrupts at the bus bridge, allowing it to use a single system IRQ for multiple PCI devices

PCI-Express, developed by Intel (and formerly know as 3GIO or 3rd Generation I/O), looks to be the "next big thing" in bus technology. At first, faster buses were developed for high-end servers. These were called PCI-X and PCI-X 2.0, but they weren't suitable for the home computer market, because it was very expensive to build motherboards with PCI-X. PCI-Express is a completely different beast – it is aimed at the home computer market, and could revolutionize not only the performance of computers, but also the very shape and form of home computer systems. This new bus isn't just faster and capable of handling more bandwidth than PCI

This new bus isn't just faster and capable of handling more bandwidth than PCI. PCI-Express is a point-to-point system, which allows for better performance and might even make the manufacturing of motherboards cheaper. PCI-Express slots will also accept older PCI cards, which will help them become popular more quickly than they would if everyone's PCI components were suddenly useless Future developments……….

Intel’s rival Advanced Micro Devices, Inc. (AMD) is developing HyperTransport, as the natural progression from PCI. it provides two point-to-point links. Each link can be anywhere from 2 bits to 32 bits wide, supporting a maximum transfer rate of 6.4 GB per second. However……. It is designed specifically for connecting internal computer components to each other, not for connecting external devices such as removable drives The development of bridge chips will enable PCI devices to access the HyperTransport bus.

Direct memory access (DMA) – This simply means that the device is configured to access system memory without consulting the CPU first. (Direct Memory Access) Specialized circuitry or a dedicated microprocessor that transfers data from memory to memory without using the CPU. Although DMA may periodically steal cycles from the CPU, data are transferred much faster than using the CPU for every byte of transfer.

DMA Disk Transfers There are various modes of data transfer on IDE disk drives. The PIO modes use the CPU, and the DMA modes bypass the CPU

DMA Used for 0 8-bit transfer 1 8-bit transfer 2 Floppy disk controller 3 8-bit transfer 4 Cascaded from bit transfer 6 16-bit transfer 7 16-bit transfer On PCs, there are eight DMA channels commonly used as follows. Most sound cards are set to use DMA channel 1 (Programmed Input/Output mode) The data transfer mode used by IDE drives. These modes use the CPU's registers for data transfer in contrast with DMA, which transfers directly between main memory and the peripheral device