Since 1978, Intel's processors have evolved from the 8086 and the 8088 to the 80286, 80386, and 80486, and then to the Pentium family of processors (which includes the Pentium, Pentium Pro, Pentium with MMX, Pentium II, Pentium III, Celeron, and Xeon processors). With the Pentium III processor, Intel achieved clock speeds greater than 500 MHz.
Advanced Micro Devices (AMD) was long known as a provider of low-performance processors for use in low-cost computers. That reputation changed in 1998, however, with the release of the K6 line of processors, which challenged Intel's processors in terms of both price and performance. With the K6-III processor, AMD broke the 600 MHz barrier, claiming the fastest processor title for the first time in IBM-compatible computers.
Cyrix began as a specialty chip maker but eventually began producing microprocessors including the MediaGX processor and now the MII series of processors.
Motorola makes the CPUs used in Macintosh and PowerPC computers. Macintosh processors use a different architecture than IBM-compatible PC processors.
PowerPC processors are RISC processors. Instruction sets for RISC processors are kept smaller than those used in CISC chips. This smaller size enables the processor to run faster and process more instructions per second. RISC processors are found in Apple microcomputers, some workstations, and many minicomputers and mainframe systems. They are also the basis for many small digital devices, such as H/PCs.
Universal Serial Bus (USB) The USB standard may someday eliminate the need for multiple types of buses in a single computer. Currently, a USB port can accept as many as 127 devices, extending the system's bus to many peripherals. The USB standard also provides for a data transfer rate of 12 Mb per second, which compares favorably to standard parallel and serial port throughput and is more than adequate for many peripheral devices.
Specifically, the USB standard provides the following advantages over traditional expansion bus designs:
No Expansion Cards. You simply plug a USB-compliant device into the computer's existing USB port. Because the computer's USB port is already built in, you do not need to add a new port to the computer by installing an expansion card.
You Can Leave Your System in One Piece. Installing an expansion boardmeans opening your computer – a daunting task for most users. Because the USB port is already built into newer systems, you may never need to remove the system's cover again.
True "Plug and Play." Whenever you add an expansion card to a computer, you may need to make other changes to enable the card to work. USB devices require no special settings, which means that the dream of true "Plug and Play" is nearly a reality. Because USB devices all adhere to the same standards, you plug the new device into the USB port, turn it on (an optional step for some devices), and start using it. The system will recognize the new device right away, which means that you will not need to reboot the computer.
Never Run Out of Ports. With traditional expansion bus technologies, you are limited to the number of available expansion slots. Once they are filled, you cannot add any other devices, unless you want to invest in a SCSI adapter and SCSI-compliant devices. (SCSI devices are considerably more expensive than non-SCSI devices.) Most USB-compliant computers have two built-in ports, each capable of supporting 127 devices at one time. To connect multiple peripherals, you can use an inexpensive USB "hub," which provides additional ports for chaining multiple devices together.
More Power and Control. The USB port supplies power to the connected devices, which means that you do not have to plug them into a power supply. Most USB devices can be controlled from the PC, so you do not have to adjust settings manually.
The USB standard is being developed through a joint effort of leaders in the computer and telecommunications industries, including Intel, Microsoft, and several others. If the standard is universally adopted (hence its name), its proponents believe that it will apply to almost any device that can be plugged into a computer, including keyboards, pointing devices, monitors, scanners, digital cameras, game controllers, printers, modems, and more.