Definitions and Meanings
(Or: Everything explained may be twice as confusing)
The following is a collection of definitions and explanations for various
terms found in the documentation for my project, "Riffer
Builds A New Computer".
Digital Storage Measurement Units
Computer memory and storage is always digital, which is to say that all
data and numbers are stored as just long strings of binary digits ("1"'s
and "0"'s). There are a number of terms that are used to refer to different
amounts of digital storage, making up the common unit names for computer
memory, disk storage, backup tape capacity, etc.
| Unit Name |
Equivalent To |
Common Abbreviations |
| Binary Digit |
Only two possible values:
"0" or "1". |
Bit |
| Nibble |
Four bits |
Nibble |
| Byte |
Eight bits |
Byte |
| Kilobyte |
1,024 Bytes |
K-Byte or KByte
K
KB |
| Megabyte |
1,024 Kilobytes |
Meg (plural "Megs")
MB |
| Gigabyte |
1,024 Megabytes |
Gig (plural "Gigs")
GB |
| Terabyte |
1,024 Gigabytes |
TB |
2X / 4X / 6X / 8X / 10X
In reference to CD-ROM drives, one of the most common distinguishers is
the speed of the drive. Any CD-ROM drive is reffered to as a "2X" or a
"6X", etc. What thisis reffering to is the speed of the drive: More specifically,
the rate at which data is transferred from the drive to the computer.
The original first CD-ROM drives had a transfer rate of 150KB
(KiloBytes) per second. Later generation drives
had twice the transfer rate and so were called "2X" drives. This trend
has continued on up to the 8X drives (which have a transfer rate of 1,200KB
per second) and beyond. The data transfer rate is significant, as no matter
how powerful a computer is, if you're waiting for data to load, your biggest
delay is the speed at which data is transferred.
RAM
RAM is an acronym for Random Access Memory, and refers to the chips that
are necessary for a computer to be able to store programs and data for
running and processing. A general synopsis about the common types of RAM
chips can be found here.
SIMM
The word SIMM is an acronym for Single In-line Memory Module. A SIMM chip
is a small circuit board, long but narrow, that has individual memory chips
on it. Depending on the SIMM type and memory size, the number of chips
can vary from 1 to 9 or more. SIMM's were developed as a more physically
compact way to add memory to a computer's motherboard.
SIMM's come primarily in two types, 30-pin and 72-pin. 30-pin SIMM's
are an older design that's max capacity tended to be 4MB per module. 72-pin
SIMM's, which are the more widely used type nowadays, can be as large as
32MB per module. However, you can only get 1MB and 2MB SIMM's in 30-pin
form.
VESA and VLB
The word VESA is an acronym for Video Electronics
Standards Association, and is actually the name of an organization
formed by various companies to establish open video standards for the PC
industry. They developed an exansion (or bus) slot standard called VESA
Local Bus (or VLB for short). This type of slot is 32-bit based (data can
be transmitted 4 bytes at a time between the CPU chip and the card in the
VLB slot), and can be used for various high-speed purposes. However, it
is primarily used for connecting high-speed video cards to the motherboard.
ISA
ISA is an acronym for Industry Standard Architecture, and was the first
type of expansion slot (or bus slot) developed for PC's, established by
IBM.
It is a 16-bit standard, so only two bytes of data can be transmitted between
the CPU chip and whatever card is plugged into the ISA slot. 16-bit slots
are fine for most purposes (soundcards, CD-ROM drives, serial & parallel
ports) but too slow for purposes such as modern high-speed video.
EISA stands for Extended Industry Standard Architecture, and is an extension
of the ISA standard, developed by independant vendors.. EISA slots can
except cards designed for ISA expansion slots, but also excepts EISA cards,
which can connect at 32-bits (able to transmit 4 bytes of data at one time).
EISA is much more expensive than ISA, however.
PCI
PCI stands for Peripheral Component Interconnect, and is the newest expansion
slot (or bus slot) standard, developed by Intel.
It is intended to be powerful and inexpensive, and unlike the other standards
can be used on non-PC platforms such as the PowerMacintosh
and digital Alpha's.
A PCI slot is 32-bit based but operates at a speed such that it can deliver
64-bit performance (8 bytes of data transmitted at a time between the CPU
chip and the card in the expansion slot).
The PCI standard is best suited for high-speed/high demand functions
such as very fast high-resolution video, hard drive controllers, and high-speed
netowrk cards. However they are relatively cheap.
Bay or Bays
In this context, a bay is the space inside a computer cabinet designed
to hold some internal peripheral of medium-to-large size. For PC's the
bays are pretty much exclusively for drives. This includes floppy drives,
hard drives, CD-ROM drives, and tape drives.
CPU
CPU is an acronym for Central Processing Unit, and refers to the chip that
is the actual "brain" of a computer. It is interchangebly used to refer
to both the actual physical chip itself, and to the entire computing unit
built around the chip (I.E. the CPU of your computer may be a box with
the monitor sitting on top of it, the modem beside it, and the printer
off to the side).
Overclocking
This term is a reference to a method used to get more performance out of
a CPU chip by driving it faster. All CPU chips operate at a specific frequency
speed, generally defined as the clock speed and measured in Megahertz.
This clock speed is determined by a tiny crystal that vibrates at a very
specific speed.
Overclocking a CPU chip means changing the motherboard configuration
(generally by arranging dip switches or sometimes by replacing the vibrating
crystal) so that the chip runs at a faster clock speed. This increases
the overall performance speed of your computer, but at a cost of producing
more heat.
A CPU chip can only be driven to a certain speed before it overheats
and will not function. Most CPU's can only have their clock speed increased
by a few percentage (ranging from 5-10 percent to maybe as much as 33 percent)
before refusing to function. Also, some CPU's become unreliable running
at a higher clock speed and will crash without warning, or cause bizarre
and unpredictable behavior. The extra heat and power level can actually
burn-out a CPU, rendering it worthless. Overclocking is risky, but not
extremely so.
USD
USD is an acronym for United States Dollars (for those not familiar with
the North American currency system). If you wish to convert the amounts
given in these pages to your native currency, check out the Olsen
& Associates Currency Converter.
RAM Cache
A RAM cache is a special repository of RAM on a motherboard that has very
quick access time. Faster access time generally makes RAM more expensive.
Most SIMM chips are used at a speed of 80ns
or 70ns. But high-speed RAM may have access times of 20ns and thus is about
four times as fast (though much more expensive).
A RAM cache "caches" (or stores) all of the data that flows in and out
of your primary system RAM. Whenever the CPU chip needs to access something
from memory it has just recently read (or written), it will access the
RAM cache first, and thus retrieve the data much faster than it would from
the primary system RAM. This increases over-all system performance, especially
with operations that involve a lot of looping of the same program code.
Even a RAM cache of as little as 8KB or 16KB can have a significant
improvement on performance. Most RAM cache's I've seen now start at a capacity
of 256KB and are also available with 512KB.
ns
The abbreviation "ns" is short for nanosecond, and is a measurement of
time. One nanosecond is one millionth of one second (or 0.000001 seconds).
Generally this is used to measure superfast operations, such as how fast
a computer can read data from RAM. A measurement such as "70ns" means that
the operation takes 70 nanoseconds.
Math Co-Processor or FPU
A math co-processor is a specialized computer chip designed specifically
to do floating-point math operations (that is, math with numbers that aren't
just whole values but have long very long fractional parts as well). Sometimes
these are also called FPU's, which is an acronym for Floating Point Unit.
A CPU chip can do mathmatical calculations much faster
than a human, but because of its nature is not able to do floating-point
math anywhere near as fast as it can deal with whole values. A math co-processor
is designed to do floating-point math quickly, and is sort of like having
a calculator for your CPU to use. Software has to be written to advantage
of a math co-procesor, but many applications already do so, and some even
requite one to be able to run.
IDE/EIDE
The word IDE is an acronym for Integrated Drive Controller. An EIDE is
an Extended Integrated Drive Controller, basically an enhancement on the
original IDE standard. The IDE controller standard allows for the usage
of hard drives that have a capacity greather then the techincal specifications
of modern PC architecture allow. IDE hard drives are the most common in
modern PC's, offering decent performance for their price. Higher performance
controllers (such as SCSI and SCSI-II controllers) are significantly more
expensive, as are the drives.
Motherboard
A motherboard is the major circuit board inside a computer that all other
circuit boards and devices connect to. The motherboard holds the
CPU
chip, the bus, the RAM, the BIOS, and
many other vital components.
Bus
The bus is that part of a motherboard that transfers data between the CPU
and expansion slots. Various lines connect the CPU to the bus, while other
lines connect the bus to the expansion slots and other parts of the motherboard.
The bus has its own clock cycle and handles all of the work of moving the
data to/from the CPU.
BIOS
The term BIOS stands for Basic Input-output Operating System. This
is special software stored on a ROM chip attached to the motherboard. Whenever
a PC is turned on, no matter what is installed on the hard drive, the first
program executed is the BIOS. And with the help of the CMOS,
the computer is able to do preliminary tests of its hardware, and then
procede to boot whatever operating system is installed on the hard drive.
The BIOS also contains basic, low-level routines to do Input/Output operations
with hardware that may be attached to the motherboard. These routines provide
just the essential ability to communicate with other components. It's up
to the operating system to do the more advanced stuff such as using a specific
protocol or standard. This also means that the OS doesn't need to know
the techincal specifics of how a particular drive controller or video card
works.
Triton Chipset
The Triton chipset is an Intel designed and manufactured set of chips that
support the Pentium CPU chip. All motherboards have to have a collection
of microchips that allow the CPU to communicate with other parts of the
motherboard, manage memory, and perform other elementary functions. Think
of these chips as the "glue" that holds all the major components and chips
together. Intel's Triton chipset is designed to be as efficient and optimal
as possible, especially in use with Pentium CPU chips.
CMOS
CMOS stands for "
Complementary Metal Oxide Semiconductor", a special low-power sort
of RAM. The CMOS holds the configuration information for a PC's hardware.
The CMOS memory allows the BIOS to
know what size hard drive you have, what communication ports are available,
how much memory is installed, etc. The CMOS is kept supplied with power
by a tiny, rechargable battery, so even if a computer is turned off for
very long periods of time, the vital configuration information is not lost.
ESD
ESD is an abbreviation for Electrostatid Discharge. Also known as static
electricity. Static electricity is very dangerous around computers, especially
individual chips. If you build up even a small charge of static electricity
in your body and then handle a computer componenet, oddds are very good
that the component will be permnately damaged or destroyed! So it is very
important to make sure you are protected against static electricity
discharges when handling bare boards and computer chips.
COAST
COAST is an acronym for Cache-On-A-Stick. It's a simple module consisting
of several high-speed RAM chips and a control chip. The module usually
has 136 "pins" on it (contact points) and is sometimes referred to as a
DIMM (Dual In-line Memory Module).
COAST modules are fitted into what are called CELP
sockets.
Frequency Units
When referring to the capabilities of video cards and monitors, many factors
are measured in frequency, I.E. how many times per second a signal may
be sent or repeated. The units for frequency are given here.
| Unit Name |
Equivalent To |
Common Abbreviations |
| Hertz |
One cycle per second |
Hz |
| Kilohertz |
One thousand cycles per second |
KHz |
| Megahertz |
One million cycles per second
One thousand Kilohertz |
MHz |
Dot-Pitch
Dot-pitch is the short name that refers to the overall resolution of the
monitor. In this case, resolution does not refer to the monitors
maximum pixel range, but the smallest image we can define on the monitor.
The inside of the picture tube of a monitor is coated with millions
of tiny dots of phospher, arranged in triad patterns of Reg, Green, and
Blue. The dot-pitch is the diagonal distance between any two phospher dots
of the same color. The shorter the difference, the lower the dot-pitch
value, and the tinier an object you can display. This also allows for crisper,
cleaner edges.
Dot-pitch values are usually given in fractions of a millimeter, but
sometimes a monitors resolution is referred to as a DPI (Dots Per Inch)
value. This measures the same thing (resolution of the display), but in
a different fashion. You should always try and find out the dot-pitch value
of a monitor, even if given the DPI.
CELP
CELP stands for Cache E L P and is a socket on a motherboard for plugging
in COAST chips to expand a motherboard's RAM cache.
ZIF
The word ZIF stands for Zero Insertion Force. It's a patented method for
inserting chips (primarily CPU chips) without having
to worry about getting everything lined up perfectly, using too much force,
or inserting the chip with unequal force. A CPU chip
is placed in a ZIF socket and a small metal arm is lowered that pulls and
pushes the chip into its appropiate location.
Last Modified: April 27th, 1997
Jeff The Riffer aka Jeff Mercer / riffer@afn.org