Abit IT5E Series User Manual page 24

2-12
The real operation clock within the CPU is the multiple of the external
clock. We refer to this factor as the clock multiplier factor. The four
factors possible are 1.5, 2, 2.5 and 3. The factor differs from one CPU
to another. For instance, the Intel Pentium 166 CPU has a 66MHz
external clock, with a multiplier factor of 2.5, so that the speed of the
internal clock is 66MHz x 2.5.
Internal clock
Also referred to as the real internal CPU clock, it is the actual internal
operating clock of the CPU. The Internal Clock is a multiple of the
external clock and of the clock multiplier factor. For instance, the Intel
Pentium 90 CPU has a 60MHz external clock and its clock multiplier
factor is 1.5; the Intel Pentium P133 CPU has a 66MHz external clock
and its clock multiplier factor is 2.
Internal CPU clock = clock multiplier factor x external CPU clock
AT Bus clock
Also referred to as ISA SPEED, or AT CLOCK, or even ISA Bus
clock. Ten years ago, the original specification of AT Bus clock
installed in the first generation PC/AT computers was 8MHz, this
means that there are some interface cards which can only work at
8MHz. In order to guarantee compatibility with older hardware, we
still support 8MHz AT Bus clock, but if your interface card is newer
or faster, you can choose a higher speed for the AT Bus clock, in
order to increase the transmission rate of the interface cards. But we
recommend you not to be too ambitious. An 8MHz setup ensures
maximum compatibility.
CPU Voltage - Vcore and Vio
From the voltage point of view, 586 series CPU can be divided into
two categories: single voltage CPU and dual voltage CPUs. Single
voltage CPUs include: Intel Pentium P54C series, AMD-K5 and Cyrix
6x86, etc.
Dual voltage CPUs include: Intel P55C with MMX, future AMD
CPUs, Cyrix 6x86L and M2.
The voltage of dual voltage CPUs has two components: Vcore and
Vio. Vcore provides all the power for internal processing, and its
power consumption is quite important. Vio provides the power
necessary for the external interface of the CPU.
Chapter 2