Frequency/Voltage Control - TYAN Tomcat i925X S5130 User Manual

Tomcat i925X S5130

3.10 Frequency/Voltage Control

This section facilitates controlling the CPU clock and frequency ratio.
CPU Clock Ratio
The CPU clock ratio setting defines how fast the CPU clock runs relative to the bus speed.
TYAN does not recommend changing this setting from the default setting. Enter any integer
value between 8 and 50. The default is 8x.
Auto Detect DIMM / PCI Clk
This BIOS feature determines whether the BIOS should actively reduce EMI (Electromagnetic
Interference) and reduce power consumption by turning off unoccupied or inactive expansion
slots.
When enabled, the BIOS will monitor AGP, PCI and memory slots and turn off clock signals to
all unoccupied and inactive slots.
When disabled, the BIOS will not monitor AGP, PCI and memory slots. All clock signals will
remain active even to unoccupied or inactive slots.
It is recommended that you enable this feature to save power and reduce EMI.
Enabled / Disabled
Spread Spectrum
This BIOS feature allows you to reduce the EMI of your motherboard by modulating the
signals it generates so that the spikes are reduced to flatter curves. It achieves this by varying
the frequency slightly so that the signal does not use any particular frequency for more than a
moment.
The BIOS offers various levels of modulation. The greater the modulation, the greater the
reduction of EMI.
In most conditions, frequency modulation via this feature should not cause any problems.
However, system stability may be slightly compromised in certain situations. For example, this
BIOS feature may cause improper functioning of timing-critical devices like clock-sensitive
SCSI devices.
Spread Spectrum can also cause problems with over clocked systems, especially those that
have been taken to extremes. Even a slight modulation of frequency may cause the processor
or any other over clocked components of the system to fail, leading to very predictable
consequences.
Therefore, it is recommended that you disable this feature if you are over clocking your system.
The risk of crashing your system is not worth the reduction in EMI. Of course, if EMI reduction
is important to you, enable this feature by all means. But you should reduce the clock speed a
little to provide a margin of safety.
Disabled / -0.5% / -0.75% / -1.00% / +/-0.125% / +/-0.250% / +/-0.375% / +/-0.500%
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Chapter 3: BIOS Setup