[-gnl-]

& also, What is the exact speed difference between PCI & ISA expansion slots?
please put the sources thanks !! cant understand the description at the net o_______o its soo deeep XD

[dabrain]

if i recall correctly the isa bus (which is like the "infrastructure" ... think of it like highways) runs with 16bit and 8mhz. the pci bus (not the same as pci-express or pci-x) runs with 32bit (pci-x is 64bit) and 33mhz.

difference?
i ll try to explain as simple as possible
the bandwidth of the isa bus is 8 bit. compare it to a 2 line highway. 8mhz is like a 30 mph speed limit
then the pci bus is like a 4 line highway with a speedlimit of 75mph (relation doesnt really match here)

hope that helped a bit

[-gnl-]

yay thank you so much
but one more question, how come it has two speeds? a bit and a mhz? D:

[birthdaycakes]

So first of all, you need to know what a bus is.

When you hit a key on your keyboard, it sends a signal that is interpreted by your computer to be a certain key, and you will see the result of pushing that key on your screen. That little electronic signal is important--the transference of that information from input (you pushing it) to output (what you see on your screen) occurs along a bus.
Another way of looking at it is like a map. The signal from the keyboard needs to be interpreted and processed by (you guessed it) the CPU. The bus provides a way for your keyboard's signal to reach the CPU, where it is processed, and then it is transferred outward. In a way, it is like a little electronic information highway.
That's....a very simplified explanation, but it's enough so you'll get the basic idea. If you look at a diagram of a very simple computer, you will see how everything is connected. There are plenty of these diagrams on the internet, so a quick search should pull one or two up for you.

Most computers have a system bus, which connects the processor to the system memory, and a PCI bus, which connects the PCI devices to the system bus. The system bus, just for reference, is much faster than the PCI bus. As far as speed, PCI operates at 33Mhz. To get the other speed which you are referencing, here is some math for you: 33Mhz x 4 bytes = 132MB/s
** 4 bytes = 32 bits; this is limited to 32 bits if you have 32 bit PCI
Bandwidth is typically expressed in MB/s, so the maximum amount of data you can transfer through PCI is 132MB/s (this is just a theoretical value, however).
PCI-X is 64 bit PCI and improves dramatically upon the bandwidth allotment.

Here are a couple places with tables of the speeds of various types of IO buses. ISA is just an older technology, but it is still very important today, so just keep that in mind. I don't really have a lot of time to explain much more, but if you read enough, eventually it might start to make sense.

http://computer.howstuffworks.com/pci3.htm
http://www.pcguide.com/ref/mbsys/buses/funcBandwidth-c.html