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Here's a few glossary-type descriptions for common terms used on this board, organized as follows:

Chip Making terminology
CPU and System architecture terms
Memory terms

Note that these descriptions are not meant to be rigorously correct, but rather good enough for someone who is not an expert.


Chip Making terminology

die: a single "chip" (cut from a wafer); denoted in size as the area in square millimeters, such as 120mm^2 (which might be a rectangle 12mm by 10mm)

wafer: a disk of silicon (highly pure and polished) to grow chips on. A wafer might contain 100-300 die. A wafer is now typically 8 inches (200mm) in diameter; Intel has just started using 12 inch (300mm)

ingot: A large, sort of, hot dog-shaped crystal of silicon. It is thinly sliced (like a pepperoni) into wafers and sent to a FAB.

yield: the percentage of dice from a wafer that are "good." A 60% yield would mean that 40% had flaws and/or failed in some manner.

FAB: A factory that makes chips; a new FAB today costs around $2 billion and can process about 5000 wafers per week.

lithography: the process of shining light (or other smaller electromagnetic waves) onto a wafer to enable the chemical etching of a chip's circuitry.

process technology: the combination of the various lithography and chemical processes that do the etching and growing of a chip's circuits; typically denoted by the width of the smallest transistor that can be produced (not exactly a precise definition). Today 0.18 microns is common and 0.13 is also in production. Each company has a specific process technology that they have developed or licensed.

transistor: A basic electronic circuit that, essentially, is an on-off switch. All logic circuits and caches are made up of combinations of transistors, A modern CPU contains tens of millions of transistors.

switching time: the time it takes a transistor, on a given process technology, to reliably go from on to off or off to on. Smaller transistors switch faster.

Copper process: a "minor" change to how chips are made, using copper instead of aluminum for interconnects. Advantage is less resistance, thus less power required and less heat produced, therefore the chip can be made to go faster without failing due to overheating.

SOI: silicon on insulator; another minor process change, allowing for lower power, less heat, thus faster switching, etc. Costs a little more for the wafers and more to process.

low-K: low-K dielectrics; another minor process change where materials with a low conductivity constant are used. This better signal insulation means less power is required and less heat is produced, etc. Of course, it costs more.

CPU and System architecture terms

SIMD: Single instruction multiple data; a general term for using a single CPU instruction to perform the same operation on many (2, 4, 8, 16 etc.) data items all done at once. SIMD is very useful in multimedia (audio and video) and 3D games, where lots of data is operated on in the same manner.

MMX: officially means nothing, (Intel trademarked term), but some have called it matrix math extensions or multimedia extensions. Simply put it is a group of low level instructions that process 64-bit SIMD integer data. For example, four 16-bit integers could be added at once. (Added in Pentium w/ MMX and Pentium II)

SSE: Streaming SIMD Extensions (Intel term); a new group of SIMD instructions that operate on 128-bit SIMD data, mostly groups of four 32-bit floating point data items. (Added in Pentium III)

SSE2: Streaming SIMD Extensions 2 (Intel term);a new group of SIMD instructions that operate on 128-bit SIMD data, mostly groups of two 64-bit floating point data and 2 (64-bit), 4 (32-bit), 8 (16-bit) or 16 (8-bit) integers. (Added in Pentium 4)

3DNow: AMD term for SIMD instructions that operate on two 32-bit floating point data items at once. The 3D comes from the fact that three dimension processing (popular in games) requires the use of lots of floating point calculations. (Added in K6-2)

3DNow Pro: AMD term for SSE. (Added for Athon XP)

ALU: arithmetic logic unit; a part of a CPU that performs integer arithmetic, such as adding.

FSB: Front Side Bus. The bus that connects the CPU to the Northbridge chip. Typically runs at 100 Mhz or 133 Mhz. On the Pentium 4 it runs at 100 Mhz (now 133 Mhz) but sends data 4 time per clock, thus it is said to be 400 Mhz or 533 Mhz.

integer: positive and negative whole numbers. An 8-bit signed integer, for example, can range from -128 to +127. An 8-bit unsigned integer can range from 0 to 255.

floating point: A numeric representation where numbers can have a decimal point and an exponent (similar to scientific notation), such as 3.5 x 10^5 (three point five times ten to the fifth power). The decimal point is said to be "floating" since its position can vary (mathematically), unlike in integers where it is always in the rightmost position.

cache: because memory operates very slow compared to CPUs, CPUs keep copies of recently used memory in a much faster (and expensive) memory closer to the CPU called a cache. The L1 (level one) cache is smaller and faster than the L2 (level two) cache. Typically the L2 cache contains both code and data, but the L1 cache has two parts, an L1 code cache and an L1 data cache. L1 caches can be 10-20 times faster than memory, L2 caches about 3-5 times faster.

Memory terms

DRAM: Dynamic Random Access Memory. The general type of memory used for the main memory in a computer system. A typical desktop system has 64 MB or megabytes (roughly a million bytes) up to 256 MB.

SDRAM: Synchronous DRAM. The most common type of DRAM over the past ~6 years. Now the slowest common type, running at 66 Mhz, 100 Mhz and 133 Mhz (Previous types: BEDO DRAM, EDO DRAM, FPM DRAM, etc.)

DDR SDRAM: Double Data Rate SDRAM. A type of SDRAM that sends data two times on every clock. 133 Mhz memory is said to be 266 Mhz.

RDRAM: Rambus DRAM (also DRDRAM for Direct Rambus DRAM). A type of DRAM that uses a completely different signaling method, with much faster signals, but fewer signals. PC800 RDRAM runs at 200 Mhz, with quad signalling, thus the 800 number.

SIMM: Single in-line memory module. A description of a small memory card with a I/O connections on a single side of the card. Which type you use is dictated by the motherboard design.

DIMM: Dual in-line memory module. Memory card with a I/O connections on both sides.

RIMM: RDRAM in-line memory module. A RDRAM meory card.

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