Abit SM5 User Manual page 20

2-12
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