| | | |  DIMM | | | | Dual In-line Memory Module. A number of RAM (Random Access Memeory) ICs (Integrated Circuits) fitted to a small PCB (Printed Circuit Board) typically fitted into a connecting slot on the motherboard of a PC. Differing from the SIMM (Single In-line Memory Module) in having a 64-bit path to the memory chips as opposed to the SIMM's 32-bit one. More modern processors such as the Pentium series with a 64-bit bus width require that SIMMs be fitted in matched pairs, whereas DIMMS can be fitted singly. Electrical contacts on either side of the SIMM are redundant (i.e. duplicated) whereas in the DIMM both sides are separate and active. Over time the DIMM has evolved from a 72-pin board using DRAM and EDO DRAM, through 100, 144, 168, 184, 200 and currently 240-pin DDR2 SDRAM and beyond. Part of
the naming convention for DIMMs includes the data width of the chips used in bits - this is usually shown in the form "x4" (by 4) or "x8" (by 8) for example - it refers to how the memory controller addresses the ICs, for example a 72-bit memory controller will need to address both sides (Ranks) on a 36-bit x4 board at the same time whereas with a 72-bit x8 one it only needs to address one side at a time to access or write data. Data rates have
increased from a mere 66MHz PC66 to PC2-6400 with an 800MHz data rate and more. Likwise the form factor of the DIMM has changed to match that of the hardware it is being fitted to: initially as much as 1.7" high, the size of the PCB has been shrunk over the years, driven partly by the server market, so that now DIMMS a mere 18.3mm high are used in many blade servers. | | | | | | CMOS | | | | Complementary Metal Oxide Semiconductor. This term, "metal oxide semiconductor" refers to the physical structure found in some field effect transistors - a metal gate electrode set on top of an oxide insulator, on top of a semiconducting material. A very widely used silicon and germanium based integrated circuit (IC) design, almost ubiquitous across all electronic products - most modern chips (termed "die" or "dice" in the industry) are now constructed on the CMOS basis. The CMOS IC is a type of transistor that, unlike other transistors, uses a combination of both NMOS (negative polarity) and PMOS (positive polarity) circuits connected together. Only one of these circuit types is on at a particular time (CMOS circuits dissipate power only when switching), meaning that a CMOS chip uses less power than an equivalent NMOS or PMOS chip and is very efficient, also emitting less energy in the form of waste heat. As a result of the latter, certain CMOS chips can run very fast without risking heat damage. CMOS circuitry is more dense than other design types with the same functionality. The charge in the circuit can also stay in one state over an extended period of time. CMOS circuits also show a high level of immunity to electronic noise. All of this makes CMOS ICs ideal for use in battery powered devies such as laptop PCs and PDAs for example. CMOS memory is also used in PCs (and other devices) to store critical low-level system information such as system setup data and the time and date, where the minimal current drain on a small lithium ion "CMOS battery" on a motherboard (for example) can keep this data safe for many years. | | | | | | Gateway | | | | A software or hardware device that acts to bridge two or more networks and acts as an "entrance", allowing information to be shared between computers. Strictly, it means a hardware or software device forming a node (a "processing location" such as a PC or printer that has a unique MAC address) in a network, that connects two networks using either different protocols or different applications, however it can also refer to a device linking two similar networks in which case it acts simply as an entrance or exit point. In the former case, it converts data packets from one protocal to another and in the latter it allows the connecting networks to share information by converting data and/or commands between different formats. In general usage however, the term has come to mean any system that allows access to another. A common example of the use of a gateway in the home is an ISP connecting the user to the internet. When accessing a website from a PC data may pass through a large number of gateways in the processs. A gateway may be combined with a router and/or a switch within the same hardware device, which may be relatively inexpensive, particularly in devices intended for home use and small business networks. In the case of enterprise level business applications, it may take the form of a server acting as a gateway/node and also as a firewall and proxy server. This term used to be used to describe a router but is now obsolete in that sense. | | | |
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