(1) A collection of wires through which data is transmitted from one part of a computer to another. You can think of a bus as a highway on which data travels within a computer. When used in reference to personal computers, the term bus usually refers to internal bus. This is a bus that connects all the internal computer components to the CPU and main memory. There's also an expansion bus that enables expansion boards to access the CPU and memory.
All buses consist of two parts -- an address bus and a data bus. The data bus transfers actual data whereas the address bus transfers information about where the data should go.
The size of a bus, known as its width, is important because it determines how much data can be transmitted at one time. For example, a 16-bit bus can transmit 16 bits of data, whereas a 32-bit bus can transmit 32 bits of data.
Every bus has a clock speed measured in MHz. A fast bus allows data to be transferred faster, which makes applications run faster. On PCs, the old ISA bus is being replaced by faster buses such as PCI.
Nearly all PCs made today include a local bus for data that requires especially fast transfer speeds, such as video data. The local bus is a high-speed pathway that connects directly to the processor.
Several different types of buses are used on Apple Macintosh computers. Older Macs use a bus called NuBus, but newer ones use PCI.
(2) In networking, a bus is a central cable that connects all devices on a local-area network (LAN). It is also called the backbone.
A computer, software product, or device that functions exactly like another, better-known product. In practice, the term refers to any PC not produced by one of the leading name-brand manufacturers, such as IBM and Compaq.
Abbreviation of central processing unit, and pronounced as separate letters. The CPU is the brains of the computer. Sometimes referred to simply as the processor or central processor, the CPU is where most calculations take place. In terms of computing power, the CPU is the most important element of a computer system.
On large machines, CPUs require one or more printed circuit boards. On personal computers and small workstations, the CPU is housed in a single chip called a microprocessor.
Two typical components of a CPU are: The arithmetic logic unit (ALU), which performs arithmetic and logical operations. The control unit, which extracts instructions from memory and decodes and executes them, calling on the ALU when necessary.
Another name for a chip, an IC is a small electronic device made out of a semiconductor material. The first integrated circuit was developed in the 1950s by Jack Kilby of Texas Instruments and Robert Noyce of Fairchild Semiconductor.
Integrated circuits are used for a variety of devices, including microprocessors, audio and video equipment, and automobiles. Integrated circuits are often classified by the number of transistors and other electronic components they contain:
Short for Level 2 cache, cache memory that is external to the microprocessor. In general, L2 cache memory, also called the secondary cache, resides on a separate chip from the microprocessor chip. The Pentium Pro, however, has an L2 cache on the same chip as the microprocessor
A silicon chip that contains a CPU. In the world of personal computers, the terms microprocessor and CPU are used interchangeably. At the heart of all personal computers and most workstations sits a microprocessor. Microprocessors also control the logic of almost all digital devices, from clock radios to fuel-injection systems for automobiles.
Three basic characteristics differentiate microprocessors:
Instruction set: The set of instructions that the microprocessor can execute.
bandwidth : The number of bits processed in a single instruction.
clock speed : Given in megahertz (MHz), the clock speed determines how many instructions per second the processor can execute.
In both cases, the higher the value, the more powerful the CPU. For example, a 32-bit microprocessor that runs at 50MHz is more powerful than a 16-bit microprocessor that runs at 25MHz.
In addition to bandwidth and clock speed, microprocessors are classified as being either RISC (reduced instruction set computer) or CISC (complex instruction set computer).
A set of 57 multimedia instructions built into Intel's newest microprocessors and other x86-compatible microprocessors. MMX-enabled microprocessors can handle many common multimedia operations, such as digital signal processing (DSP), that are normally handled by a separate sound or video card. However, only software especially written to call MMX instructions -- so-called MMX-enabled software -- can take advantage of the MMX instruction set.
The first generation of computers with MMX chips hit the market in January, 1997.
(1) A technique used in advanced microprocessors where the microprocessor begins executing a second instruction before the first has been completed. That is, several instructions are in the pipeline simultaneously, each at a different processing stage.
The pipeline is divided into segments and each segment can execute its operation concurrently with the other segments. When a segment completes an operation, it passes the result to the next segment in the pipeline and fetches the next operation from the preceding segment. The final results of each instruction emerge at the end of the pipeline in rapid succession.
Although formerly a feature only of high-performance and RISC -based microprocessors, pipelining is now common in microprocessors used in personal computers. Intel's Pentium chip, for example, uses pipelining to execute as many as six instructions simultaneously.
Pipelining is called pipeline processing.
(2) A similar technique used in DRAM, in which the memory loads the requested memory contents into a small cache composed of SRAM and then immediately begins fetching the next memory contents. This creates a two-stage pipeline, where data is read from or written to SRAM in one stage, and data is read from or written to memory in the other stage.
DRAM pipelining is usually combined with another performance technique called burst mode. The two techniques together are called a pipeline burst cache.
A 32-bit microprocessor introduced by Intel in 1993. It contains 3.3 million transistors, nearly triple the number contained in its predecessor, the 80486 chip. Though still in production, the Pentium processor has been superseded by the Pentium Pro and Pentium II microprocessors.
Intel's newest member of the Pentium chip family. The Pentium II builds on the design of the Pentium Pro, but adds an additional 2 million transistors to bring the total up to 7.5 million. Current versions of the chip run at speeds of 233, 266, 300, and 333 MHz. In addition, the Pentium II features the following:
A Singled Edge Contact (SEC) cartridge that fits into Slot 1
Dual Independent Bus (DIB) architecture
512K L2 cache
32K L1 cache
MMX support
The Pentium Pro is Intel's sixth generation microprocessor (P6). Although, it shares the same name as the fifth-generation Pentium microprocessor, the Pentium Pro is architecturally quite different. Thanks to modern design techniques, including superpipelining, dynamic execution, and on-chip L2 cache, the Pentium Pro can perform at nearly twice the speed of previous Pentium microprocessors.
Refers to microprocessor architectures that enable more than one instruction to be executed per clock cycle. Nearly all modern microprocessors, including the Pentium, PowerPC, Alpha, and SPARC microprocessors are superscalar.
The bus that connects the CPU to main memory. As PC microprocessors have become faster and faster, the system bus has come under increased scrutiny as one of the chief bottlenecks in modern PCs. With the advent of the Pentium microprocessor, the older system bus speed of 33 MHz was doubled to 66 MHz. But microprocessor speeds raced ahead to over 300 MHz. This meant that system designers needed to insert up to 5 wait states between each memory access.
In 1998, Intel introduced a new Pentium II chipset (the 440BX) that increases the system bus speed to 100 MHz.
A device composed of semiconductor material that amplifies a signal or opens or closes a circuit. Invented in 1947 at Bell Labs, transistors have become the key ingredient of all digital circuits, including computers. Today's microprocessors contains tens of millions of microscopic transistors.
Prior to the invention of transistors, digital circuits were composed of vacuum tubes, which had many disadvantages. They were much larger, required more energy, dissipated more heat, and were more prone to failures. It's safe to say that without the invention of transistors, computing as we know it today would not be possible.