<Original Answer> because some devices on the board are slower than others and do not require or cannot support the same bus speeds.
<Update> The book that this question comes from has another answer: that it is required for backwards compatibility. This is the answer for the test, but, I do not like it.
My answer is that having a high speed bus to some devices is a waste of CPU effort that could be better used on RAM or other high-speed items. There is not point to putting a modem or printer on a high speed bus that the CPU has to monitor only to find out that the printer or modem is done with the last burst of data sent.
It makes compatible with low price memory and result wider market for the motherboard itself.
yes
Yes, you can have as many as your case and motherboard will support.
No.
The faster the CPU can push data around the motherboard is mesured as a frequency
The Asus motherboard 77-12dl will be more than enough for your tpical home setup.
Yes.
Because the motherboard/processor is designed with that speed in mind, so overheating and various other issues can occur much more frequently at higher speeds. Also, the process of running hardware at a higher speed than is standard is called overclocking.
A server mother is like a normal motherboard except they are geared to a server processor and can hold more than one processor usually. They also support ECC memory which is memory with error correction. They support RAID. And most can are slim to be put in what is called a U1 chassis so they can go on a server rack.
The processor size or speed does not determine how much RAM your system needs. Generally speaking, the newer the system, the more RAM you can add. The amount of RAM slots on a motherboard and the motherboard's own subsystem (the BIOS) will determine how much RAM you can add to a particular motherboard.
You can buy more RAM for your computer. It can speed up your computer depending on your memory usage. You can buy it at a local electronics store. RAM only improves a computer's speed to a certain point, at which motherboard components and processor speed limit computer performance. So the question is oversimplified as computer speed is governed by motherboard chipsets, processor core numbers and speed, RAM volume, hard drive writing speed, etc.
It depends on your motherboard. It likely uses either DDR or DDR2 memory, and the speeds that are supported vary by the make and model of your motherboard. It doesn't support more than 4gb of RAM.