What is clocking?
The CPU works on two frequencies: An internal and an external.
The external clock frequency (the bus frequency) is the speed between the CPU and RAM. In the Pentium CPU's it is
actually the speed between L1 and L2 cache. In the Pentium II it is the speed between L2 cache and RAM.
l The internal clock frequency is the speed inside the CPU, that is between L1 cache and the various CPU registers.
For practical reasons you let these two frequencies depend on each other. In practice you choose a given bus frequency
(between 60 and 100 MHz) and double it up a number of times (between 1½ and 5). The latter frequency become the CPU
internal work frequency.
Here I show a number of theoretical CPU frequencies, resulting form different clock doublings: Many of these frequencies
will actually never be used, but they are possible because of the system structure:
Note an important point:
The CPU frequency is the result of the the bus frequency multiplied with a factor. If you increase the
bus frequency, it affects the CPU frequency, which is also increased.
Look here at a page from the manual to a ASUS P2L97 motherboard. It has a clear instruction about how to set the the two
values (bus frequency and clock factor). This motherboard accepts bus frequencies up to 83 MHz with a clock factor up to 5:
The CPU works on two frequencies: An internal and an external.
The external clock frequency (the bus frequency) is the speed between the CPU and RAM. In the Pentium CPU's it is
actually the speed between L1 and L2 cache. In the Pentium II it is the speed between L2 cache and RAM.
l The internal clock frequency is the speed inside the CPU, that is between L1 cache and the various CPU registers.
For practical reasons you let these two frequencies depend on each other. In practice you choose a given bus frequency
(between 60 and 100 MHz) and double it up a number of times (between 1½ and 5). The latter frequency become the CPU
internal work frequency.
Here I show a number of theoretical CPU frequencies, resulting form different clock doublings: Many of these frequencies
will actually never be used, but they are possible because of the system structure:
Note an important point:
The CPU frequency is the result of the the bus frequency multiplied with a factor. If you increase the
bus frequency, it affects the CPU frequency, which is also increased.
Look here at a page from the manual to a ASUS P2L97 motherboard. It has a clear instruction about how to set the the two
values (bus frequency and clock factor). This motherboard accepts bus frequencies up to 83 MHz with a clock factor up to 5:
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