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Celeron™ Processor Development Kit Manual
4-11
Hardware Reference
4.7 Jumpers
Table 4-13 shows default Jumper settings.
4.7.1 Enable Spread Spectrum Clocking (J14)
This jumper is used to enable or disable spread spectrum clocking on the clock synthesizer. When
this jumper is in, a 0.5% down spread will be introduced into the PCI and processor clocks. The
default setting is no jumper installed, which disables spread spectrum clocking.
4.7.2 Clock Frequency Selection (J15)
This jumper controls the frequency of the processor clock. When the jumper is in, 66 MHz
operation is supported. This is the only setting supported by this evaluation kit.
Caution: Leave this jumper installed. When the jumper is out, 100 MHz processor clocks will be generated.
This position is not supported and may cause damage to the processor.
4.7.3 On/Off (J20)
This jumper is used to control the state of the ATX power supply. When this jumper is removed, the
power supply will be turned off. Placing the jumper in the 2-3 position will turn the power supply
on.
The 1-2 position is reserved and should not be used.
Table 4-13. Default Jumper Settings
Jumper Function Settings
J14 Enable Spread Spectrum Clocking
In – Enable Spread Spectrum
Out – Disable Spread Spectrum (Default)
J15 Clock Frequency Selection
In – 66 MHz Processor Clock (Default)
Out – Reserved
J20 On/Off
1–2 Reserved
2–3 On (Default)
No Jumper Installed – Off
J21 Flash BIOS VPP Select
1–2 12 V
2–3 5 V (Default)
J22 Flash BIOS boot block control
1–2 12 V
2–3 5 V (Default)
J23 SMI# Source
1–2 SMI# controlled by IOAPIC
2–3 SMI# controlled by PIIX4E (Default)
J24 CMOS RAM Clear
1–2 Normal Operation (Default)
2–3 Clear CMOS RAM