Advantech IPPC-7157 Series, User Manual

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59 Chapter 4
4.9 Frequency/Voltage Control
Run the Frequency/Voltage Control as follows:
1.
Choose“Frequency/Voltage Control”from the Main Menu and a list
of options will appear.
2. Use one of the arrow keys to move between options and modify the
selected options by using PgUp / PgDn / + / - keys.
Auto Detect DIMM/PCI CLK
To reduce the occurrence of electromagnetic interference (EMI), the
BIOS detects the presence or absence of components in DIMM and PCI
slots and turns off system clock generator pulses against empty slots.
Spread Spectrum
When the system clock generator pulses, the extreme values of the pulse
generate excess EMI. Enabling pulse spectrum spread modulation
changes the extreme values from spikes to flat curves, thus reducing EMI.
This benefit may in some cases be outweighed by problems with timing-
critical devices, such as a clock-sensitive SCSI device.
A u to D e c t D IM M /P C I C lk E n a b le d Ite m H e lp
S p r e a d S p e c tr u m
E n a b le d M e n u L e v e l