AGP (Accelerated Graphics Port) Intel's AGP specification describes a high-speed point-to-point connection between a computer's graphics controller and the chipset. It bypasses the slower PCI bus. Older desktops supported AGP 1X (264-MBps transfer rate) and AGP 2X (528 MBps), but newer systems support AGP 4X (1.056 GBps) and 8x (2.1GBps)
ATA (AT Attachment) This is a standard for connecting mass-storage devices such as hard drives, CD-ROM drives, and tape drives to a PC. Although there are slight differences in the specification, ATA is used interchangeably with IDE.
Bus A bus is a collection of electrical lines that carry data (one bit per line), power, or a combination and to which multiple devices, such as expansion cards, can be connected.
Cable modem This is a communications device that transmits data over cable-TV lines at speeds of 1 MBps to 10 MBps and connects to your computer via Ethernet.
Cache A cache is high-speed memory that normally resides in the processor and holds the most recently used data for quick retrieval. Most processors have Level 1 (primary) and Level 2 (secondary) caches. Level 3 is found in some server processors and in Intel's P4 EE.
CD-ROM These optical discs store prerecorded digital data in read-only form and are most often used by publishers for distributing programs, data, music, or graphics.
CD-R CD-R media are optical discs that can be recorded on by the end user, but cannot be erased. A CD holds 74-80 minutes of audio or about 650MB of data.
CD-RW Optical discs that are the same as CD-Rs in capacity but can be recorded on and erased numerous times.
Chipset A chipset is a group (generally) of separate integrated circuits that control the flow of information among the components on the motherboard.
CPU (central processing unit) This integrated circuit is the brains of a modern computer. The CPU contains the arithmetic and logic hardware that does the bulk of the information processing. Also referred to as the processor.
DDR SDRAM (Double Data Rate SDRAM) This memory is similar to SDRAM, but is twice as fast at the same clock speed. It accesses data two times per clock cycle; SDRAM accesses data only once per cycle. DDR memory is available at effective (meaning the clock runs at half this speed but transfers data like DRAM at the rated speed) speeds of 200 to 550 MHz.
DDR2 SDRAM (2nd generation Double Data Rate SDRAM) Like DDR, except it uses an increased number of data prefetch buffers. The buffers double the amount of data transferred per clock cycle to four. But the internal core clock cycle is reduced by half to save power, which negates the gains achieved by the increase in buffers, giving the same throughput as DDR at the same clock speed. Because of DDR2's lower power consumption, though, vendors will be able to ramp up its speed beyond DDR's capabilities. DDR2 memory is available at speeds of 400 MHz and 533 MHz, with 667 MHz expected late this year.
DIMM (Dual Inline Memory Module) A small circuit board with memory chips mounted on both sides. The bottom edge of a DIMM has electrical contacts printed on it, and plugs into a special connector that is usually on the motherboard.
Dual-layer DVD+/-RW (Dual Layer DVD Plus/Dash Rewritable) As the name implies, there is a second layer to read data from and write it to, so this disk can hold up to 8.5GB of data. It will read and write everything just like a DVD+-RW drive, but dual layer is currently only a DVD+ format. These are relatively new drives, but their prices have dropped precipitously, and now they are in many desktops, even budget ones. Dual-layer discs are still pricey, at $10 each.
DMA (Direct Memory Access) This is a method of moving blocks of data between a storage device and memory without utilizing the CPU. (See Ultra DMA.)
DRAM (Dynamic Random Access Memory) A form of RAM. DRAM temporarily stores data and instructions used by the CPU (and other devices). The term dynamic in this acronym refers to the need to constantly refresh the contents of this type of memory, meaning it only "remembers" when the power is on.
DVD (Digital Versatile Disc or Digital Video Disc) These optical discs, the same physical size as a CD, hold much more data than a CD. A standard DVD can hold about 4.7GB of data or 133 minutes of a movie.
DVD-RAM A different format than DVD, this type of DVD can be recorded to, erased, and rewritten many times. Many drives require the disc to be held in a cartridge. A standard DVD-RAM can hold about 4.7GB of data.
DVD-ROM (DVD Read-Only Memory) These discs are read-only and can hold about 4.7GB of data or 133 minutes of a movie. They are used for distribution of large programs, movies, music, data, and more.
DVD-RW (DVD Dash Rewritable) This is a DVD drive with all the capabilities of a DVD-ROM drive and the ability to write to DVD-R and DVD-RW media. DVD-RW drives are all but gone in new PCs, but older ones may still have them. You have to watch for compatibility problems, since they won't read or write to DVD+R or DVD+RW media.
DVD+RW (DVD Plus Rewritable) This is a DVD drive with all the capabilities of a DVD-ROM drive and the ability to write to DVD+R and DVD+RW media. Like DVD-R drives, DVD+R drives are all but gone in new PCs, but older ones may still have them. They too won't read or write to DVD-R or DVD-RW media.
DVD+/-RW (DVD Plus/Dash Rewritable) Since the DVD+ Alliance and the DVD- Forum would not agree on a single standard, drive manufacturers came up with a drive that can read and write to all DVD formats (except DVD-RAM) as well as all the CD types.
ECC DRAM (Error Correction Code DRAM). ECC is a technology used in certain memory types, particularly SDRAM, that catches and corrects accidentally changed bits without stopping the system. ECC RAM costs more than non-ECC RAM, and is used in mission critical applications like workstations and servers.
FSB (Front-Side Bus) This bus connects the CPU to the memory controller chip on the motherboard. It is the main pipeline between the CPU and the rest of the system.
IDE (Integrated Device Electronics) IDE makes the controlling circuitry for mass-storage devices part of the devices themselves. This technology is the standard way of connecting hard drives, CD-ROM drives, and tape drives to a system. Although there are slight differences in the specification, IDE is used interchangeably with ATA.
IEEE 1394 (Institute for Electrical and Electronic Engineering standard number 1394) Otherwise known as FireWire, this is a high-speed serial bus used for connecting peripheral devices, such as digital camcorders. The common connection can transfer data at 400 Mbps, although the newest connection, FireWire 800, can transfer data at 800 Mbps.
Memory General term that typically refers to RAM. The processor stores the information it needs in these microchips. Other devices, especially graphics cards, often have memory of their own.
Modem A modem converts digital signals from a computer to analog signals that can be transmitted over a telephone line. It reverses the process for receiving information over the telephone line.
Motherboard This is the computer's main circuit board, on which the processor and system memory reside, as well as the chipsets that control information flow and the circuitry that connects components to the processor and each other.
PCI (Peripheral Component Interconnect). This is the standard bus architecture used in desktops today. PCI slots have direct access to system memory via a controller called a PCI bridge, use a bus that can be 32 or 64 bits wide, and have bus speeds of 33 MHz to 133 MHz. The typical PCI bus found in every desktop is 32 bits wide and runs at 33 MHz.
PCI Express (PCIe). Similar to the IDE to SATA transition, PCI's parallel connection is moving to PCI Express's serial connection. While a typical 33-MHz, 32-bit PCI bus has a unidirectional total bandwidth of 133 MBps, each pair of wires on PCIe is capable of transferring 2 Gbps in both upstream and downstream (read and write) directions for an effective total bandwidth of 4 Gbpsor 500 MBps. Since PCIe is a point-to-point serial connection, that bandwidth is available for each card connected to it, rather than being shared among all the cards as it is for PCI. These pairs of wires can also be grouped together to make x2, x4, x8, x16, and x32 (pronounced "by 2, by 4," and so on) connections, with each pairing doubling the throughput. The next generation of graphics cards will no longer be on the 8X AGP bus but on the x16 PCIe connection. Today's 8X AGP graphics bus has a unidirectional bandwidth of 2 GBps. With x16 PCIe, bandwidth is 4 GBps in each direction, for a cumulative bidirectional bandwidth of 8 GBps. It will be a slow transition, but PCIe will eventually replace PCI.
RAID (Redundant Array of Inexpensive Drives) The acronym refers to a collection of hard drives attached to a special controller that, among other abilities, can improve performance by sharing data across multiple drives (one such configuration is known as RAID 0) and improve reliability by having some drives mirror (fully duplicate) others in real time.
RAM (random access memory) RAM packs millions of data-storing electrical circuits onto a small chip. Devices can write to and read from these storage locations, and the CPU uses this memory to hold programs and data.
RDRAM (Rambus Dynamic RAM). Developed by Rambus and Intel, this is a unique form of system memory available for desktops. It works on a memory bus of between 600MHz and 800MHz. RDRAM is rare, as it proved to be more expensive and no faster than DDR SDRAM.
ROM (read-only memory) Memory containing information that can be read but not modified.
SATA (Serial ATA) This is an evolution of the IDE specification. New desktops typically have both IDE and SATA connectors. SATA uses a serial connection to the drives where IDE is a parallel connection. SATA drives start at a transfer rate of 150 MBps, with faster speeds expected this year. The SATA cable, containing a maximum of four links, is much smaller than the 80-pin flat-ribbon cable for IDE drives, and therefore allows for more airflow and better cooling.
SCSI (Small Computer System Interface) SCSI is a standard for a high-speed bus used to connect multiple peripherals such as hard drives, printers, and CD-ROM drives.
SDRAM (Synchronous Dynamic RAM). SDRAM is the most common form of desktop memory used today. SDRAM is the basis for DDR and DDR2 memory. SDRAM is synchronized with the CPU's clock, so there is little downtime when transferring data to the processor.
SIMM (Single Inline Memory Module) SIMM is almost identical to DIMM, but mounts the memory on only one side of a small circuit board. SLI (Scalable Link Interface) This is an nVidia proprietary technology for graphics cards. It takes advantage of the increased bandwidth of the PCIe architecture, and uses two graphics cards linked together. Each card works on roughly half the scene being displayed, sharing the calculations that need to be made. It's pricey, but delivers the best available 3D graphics performance.
SMART Drive (Self-Monitoring Analysis and Reporting Technology) Hard drives with SMART contain logic circuits that monitor the drives' health, providing a warning system that predicts potential drive failure.
SRAM (Static RAM) This is memory that, unlike DRAM, doesn't require its contents to be constantly refreshed in order to retain information.
Ultra ATA or Ultra DMA These are common interface protocols for hard drives. This high-speed interface can transfer data at rates of 100 MBps to 133 MBps, the maximum disk performance under the current PCI bus.
USB (Universal Serial Bus) USB is a popular connection method for linking many types of peripherals to computer systems. USB is quickly replacing serial, parallel, ps/2, and even, on some systems, monitor ports. The current standard, USB 2.0, can transfer data at up to 480 Mbps and connect as many as 127 devices. Because of its plugand-play capabilities, USB lets peripherals be plugged in and unplugged without shutting down the system. More and more devices incorporate USB portsdigital cameras, displays (especially flat-panel), keyboards, joysticks, mice, modemsand the list keeps growing. There are two compatible standards, USB 1.1 and USB 2.0. Both use the same connectors and cables. USB 2.0 has a faster transfer rate than USB 1.1.
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