| RAM RAM (random access memory) is sometimes referred to as DRAM (pronounced dee-ram) to distinguish it from static RAM (SRAM). Random access The process of beginning to read and decode a coded bitstream at an arbitrary point. RDRAM Short for Rambus DRAM, a type of Dynamic memory (DRAM) developed by Rambus, Inc. The fastest current memory technologies used by PCs (SDRAM) can deliver data at a maximum speed of about 100 MHz, RDRAM transfers data at up to 600 MHz. In 1997, Intel announced that it would license the Rambus technology for use on its future motherboards, thus making it the likely standard for memory architectures. However, a consortium of computer vendors are working on an alternative memory architecture called SyncLink DRAM (SLDRAM). RDRAM is already being used in place of VRAM in some graphics accelerator boards, but it is not expected to be used for the main memory of PCs until 1998 or 1999. Intel and Rambus are also working a new version of RDRAM, called nDRAM, that will support data transfer speeds at up to 1,600 MHz. Real time The actual time in which a program or event takes place. In computing, real time refers to an operating mode under which data is received and processed and the results returned so quickly that the process appears instantaneous to the user. The term is also used to describe the process of simultaneous digitization and compression of audio and video information. Reference picture The nearest adjacent I picture or P picture to the current picture in display order. Repeater Transparent devices used to interconnect segments of an extended network with identical protocols and speeds at the physical layer (OSI layer 1). Resolution Number of pixels per unit of area. A display with a finer grid contains more pixels and thus has a higher resolution, capable of reproducing more detail in an image. RGB (Red-Green-Blue) A type of computer color display output signal comprised of separately controllable red, green, and blue signals; as opposed to composite video, in which signals are combined prior to output. RGB monitors typically offer higher resolution than composite monitors. RJ11 Short for Registered Jack-11, a four- or six-wire connector used primarily to connect telephone equipment in the United States. RJ-11 connectors are also used to connect some types of local-area networks (LANs), although RJ-45 connectors are more common. R LLAbbreviation of Run Length Limited, an encoding scheme used to store data on newer PC hard disks. RLL produces fast data access times and increases a disk's storage capacity over the older encoding scheme called MFM (modified frequency modulation). Technically, any disk drive can use MFM, RLL, or some other encoding scheme. The one used depends on the integrate disk controller within the disk drive. RS-232C Almost all modems conform to the EIA-232 standard and most personal computers have an EIA-232 port for connecting a modem or other device. In addition to modems, many display screens, mice, and serial printers are designed to connect to a EIA-232 port. In EIA-232 parlance, the device that connects to the interface is called a Data Communications Equipment (DCE) and the device to which it connects (e.g., the computer) is called a Data Terminal Equipment (DTE). The EIA-232 standard supports two types of connectors -- a 25-pin D-type connector (DB-25) and a 9-pin D-type connector (DB-9). The type of serial communications used by PCs requires only 9 pins so either type of connector will work equally well. Although EIA-232 is still the most common standard for serial communication, the EIA has recently defined successors to EIA-232 called RS-422 and RS-423. The new standards are backward compatible so that RS-232 devices can connect to an RS-422 port. R S-422 and RS-423Standard interfaces approved by the Electronic Industries Association (EIA) for connecting serial devices. The RS-422 and RS-423 standards are designed to replace the older RS-232 standard because they support higher data rates and greater immunity to electrical interference. All Apple Macintosh computers contain an RS-422 port that can also be used for RS-232C communication. RS-422 supports multi-point connections whereas RS-423 supports only point-to-point connections. R S-485An Electronics Industry Association (EIA) standard for multi-point communications. It supports several types of connectors, including DB-9 and DB-37. RS-485 is similar to RS-422 but can support more nodes per line because it uses lower-impedance drivers and receivers. |
