BIOS, RAM, ROM, Capacity,
Transistors, Capacitors, Throughput, Bandwidth, Transfer Rates...and more...these are all
buzz words you've heard used on this site, as well as others...but you never got a
complete explanation on what they mean. Well, here I am to provide you with some
information. I'll try to add more information to this Guide weekly, each week
concentrating on a different topic. This week, special thanks goes out to Avinash Baliga
for writing 4, count em, 4 sections for this guide. Thanks Avinash!
| Binary Number System |
| Without this precious
system, there would be no computer hardware for me to test =) Computer Science revolves
around the idea that every function, every idea, and every procedure can be expressed by a
single digit, a 1 or a 0. The outcome of any given situation is either True, or False, 1
or 0. If you relate this to electricity and electrical engineering (not going to go into
great depth here), your processor can only determine one of two things, whether or not
there is any electrical current running over a tiny wire at any given point in time. It
takes a LOT of these true or false comparisons to generate that pretty little graphical
interface you see on your screen now, more than you can imagine.
|
| BIOS & POST |
| You should be quite
familiar with these terms. BIOS, an acronym meaning Basic Input Output System,
is quite self explanatory, it is the Basic I/O System which contains all information about
your system necessary for Basic Input and Output functions. Sometimes the BIOS Setup will
be referred to as CMOS Setup, however I should mention that the acronym CMOS stands for
Complementary Metal Oxide Semiconductor. A term commonly associated with a system's BIOS
is POST, or Power-On Self Test. POST is a series of tests which run before you ever see
that wonderful "Starting Windows 95" Screen. During POST, the system's key
components are examined and quickly tested for possible defects or configuration problems.
When a machine "won't POST", it has failed one or more of the initial tests made
by the BIOS and therefore an error is generated, signaling the hardware to either stop
responding or produce a text output for the user to diagnose and interpret.
|
| Bits & Bytes & Transfer Rates |
| Now I know you've used the
terms Bits, and Bytes sometime in your computer-using lifetime, most likely with some mega
or giga prefixes. But have you ever actually understood what you were talking about? Lets
simplify this, in computer science, a bit is the amount of space necessary to account for
a single comparison's outcome. Confused? A bit is the amount of space needed to store one
digit in a binary number system (see Binary Number System), a 1 or a 0. A byte then is a
combination of 8 bits, or 8 1's and 0's (i.e. 10010010). A megabyte, is the most
misunderstood measurement of storage. A kilobyte is in fact, 210 bytes, or 1024
bytes. In that case, a Kilobit (not a kilobyte) is 1/8 of a kilobyte (8 bits in a byte) or
128 bytes. Meaning that a megabyte, is 210 kilobytes, or 1024 kilobytes (KB).
In turn, a megabit is equal to 1/8 of a megabyte, or 128 kilobytes (KB). Therefore, as you
might expect, a gigabyte is equal to 210 megabytes, or 1024 megabytes.
Therefore a gigabit is 1/8 of a gigabyte, or 128 megabytes (MB). I know you've heard the
modems referred to by their maximum transfer rates, i.e. 28.8K, 33.6K, 56K etc... Lets
take a 33.6K modem for example, sometimes referred to a 33,600 bps or baud modem. The
33.6K means the modem can transfer at 33.6 kilobits not kilobytes per second. Many people
have made that mistake, and wonder why their transfer rates are so slow. Well that's why,
your 33.6K modem is transmitting and receiving data at 33.6 kilobits per second or about
34406 bits per second. Divide that number by 8, and you get a maximum transfer rate of
around 4300 bytes per second, which translates into 4.2 kilobytes per second (KB/S). You
also have to factor in net traffic and the current limitations of our analog phone lines,
but that is basically the deal behind Bits, Bytes, and Transfer Rates
|
| Bus |
| The bus is like a set of
tiny wires that are on your motherboard. They allow the processor to access RAM and to
interact with other devices, such as a graphics card, printer, sound card, hard-drive, and
anything else that's in your computer. It used to be that the bus operated at speeds
equivalent to the processor (33MHz 80386 had a 33MHz bus), but this quickly changed after
processors got to 50MHz (only 33MHz bus-speed back then). Nowadays, with processors at
200+MHz there's no way that the bus can even come close to the processor's speed. This
means that if the processor is accessing memory or an external device (on the motherboard)
the time it takes will be significantly slower than if it simply accessed it's own
internal hardware (registers, L1 cache). The bus is of an ingenious design where the
processor sends the signal to all devices and the component that is supposed to receive
the message responds, the rest ignore it. The bus is sort of like a megaphone that the
processor shouts commands through, and only the individual components the processor is
calling obey their commands. Courtesy of Avinash Baliga of Vzzrzzn's Programming Homepage
|
| Capacitors |
| You've heard everyone make
the claim that larger capacitors, and more of them make motherboards run stable...but
you've never been told why. Lets discuss, first of all, what a capacitor is. A
Capacitor is simply 2 conductive plates, separated by an insulating material. A
capacitor's main function is to store an electrical charge. The insulating material
separating the 2 conductive plates is used as a resistor, or something that resists
electrical current, and therefore is used as a sort of a regulator in this case. So what
makes more capacitors better? If used properly, more capacitors can allow motherboard
manufacturers to more accurately and more reliably control the voltages being supplied to
the CPU. Therefore increasing stability, especially during times when the voltage levels
required by the CPU become critical (i.e. when overclocking!). It is because of this that
motherboards with larger, better quality, and therefore longer lasting capacitors are much
more reliable and stable at higher bus speeds (i.e. AOpen AX5T or Megatrends HX83). In the
case of some motherboards, superb design and engineering makes it possible to overclock
some processors (like the AMD K6) without having to increase the CPU's voltage. Ever
wondered why on some motherboards in order to overclock a Pentium 133 to 166, or K6-166 to
225 you need to increase the voltage supplied to the CPU while on other boards with the
exact same chip it isn't necessary? It is somewhat due to the engineering quality of the
motherboard, was the board manufactured using high quality capacitors with stability in
mind? If the answer to that is no, then in some cases you will only receive stable
performance at overclocked speeds with a processor by increasing its core voltage. This is
not true in all situations, it depends on the placement and application of the capacitors
to determine their outcome. Just because one motherboard uses 20 capacitors and another
uses 12 doesn't mean that the latter motherboard will be less stable or less reliable. The
rule of thumb is that more capacitors near key components or ICs (see IC - Integrated
Circuit) (such as the CPU Socket, Voltage Regulators, even expansion slots!) the better
the application of the capacitors. When choosing a motherboard there are a few types of
capacitors commonly used. Although most Tantalum capacitors are sufficient for normal, and
even overclocked operation, the big bad Sanyo capacitors are what you need for a rock
solid motherboard. Companies that use Sanyo capacitors, include AOpen, ASUS and Megatrends
just to name a few. And it is because of their excellent engineering and design, as well
as proper use of high quality capacitors that their motherboards are among the best and
most reliable.
|
| Caches |
| There are currently two
types of caches, L1 (level 1) and L2 (guess...). The L1 cache is built into the processor,
so there are no bus-lines to go through; the L2 cache is an external piece, although I
understand that on Pentium II's it's attached to the plug-in card. The cache is a layer
between system RAM and your processor. Think of it like a salesperson in a department
store. If there is a model on the shelf then it will be handed to you with little hassle;
but if the shelf is empty then they will have to go to the storage area. Well the cache
keeps track of the most recently used memory addresses (locations) within it and the
values they contain. When the processor requests an access to memory (trust me, it will)
then that address and value must be in the cache. If it is not, then the cache will load
that value from memory, and replace some previously cached memory address with this new
one (if necessary). If a program is not optimized to take advantage of the cache's ability
to make repeated access to the same address, then severe performance hits result. For
instance, to speed itself up, the L1 cache on the Pentium loads strips of 32 bytes at a
time from the L2 cache. If the address the program is looking for is not in the L1 cache,
approximately 75 nanoseconds will be wasted on a P200. If this value is not in the L2
cache either, then an additional 1.5 to 2.5 microseconds will be wasted in "cache
thrashing". All this for one add instruction that uses a seldom-used RAM location!
Think about the number of adds, subtracts, and moves that are done in code. Microseconds
are certainly an insignificant measure of time for you and me, but now think about whether
your 50ns EDO RAM or your 10ns SDRAM is performing up to par! I hope I have proved my
point. Courtesy of Avinash Baliga of Vzzrzzn's Programming Homepage
|
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