10 ASUS P/I-P55T2P4S User’s Manual
III. INSTALLATION
5. CPU External (BUS) Frequency Selection (FS1, FS2)
These jumpers tells the clock generator what frequency to send to the CPU.
These allow the selection of the CPU’s External frequency (or BUS Clock). The
BUS Clock times the BUS Ratio equals the CPU's Internal frequency (the ad-
vertised CPU speed).
6. CPU to BUS Frequency Ratio (BF0, BF1)
These jumpers set the frequency ratio between the Internal frequency of the
CPU and the External frequency (called the BUS Clock) within the CPU. These
must be set together with the above jumpers CPU External (BUS) Frequency
Selection.
CPU : BUS Frequency Ratio (1.5x, 2.0x, 2.5x, 3.0x)
1.5 x
1
2
3
BF0
BF1
2.0 x
1
2
3
BF0
BF1
2.5 x
1
2
3
BF0
BF1
3.0 x
1
2
3
BF0
BF1
CPU External Clock (BUS) Frequency Selection
50MHz
123
FS2
FS1
55MHz
123
FS2
FS1
FS2
FS1
66MHz
123
FS2
FS1
60MHz
123
Set the jumpers by the Internal speed of the Intel, Cyrix, or AMD CPU as follows:
(BUS Frequency) (Freq. Ratio)
CPU Model Freq. Ratio (BUS Freq.) FS2 FS1 BF0 BF1
Intel Pentium 200MHz 3.0x 66MHz [1-2] [2-3] [1-2] [2-3]
Intel Pentium 166MHz 2.5x 66MHz [1-2] [2-3] [2-3] [2-3]
Intel Pentium 150MHz 2.5x 60MHz [2-3] [1-2] [2-3] [2-3]
Intel Pentium 133MHz 2.0x 66MHz [1-2] [2-3] [2-3] [1-2]
Intel Pentium 120MHz 2.0x 60MHz [2-3] [1-2] [2-3] [1-2]
Intel Pentium 100MHz 1.5x 66MHz [1-2] [2-3] [1-2] [1-2]
Intel Pentium 90MHz 1.5x 60MHz [2-3] [1-2] [1-2] [1-2]
Intel Pentium 75MHz 1.5x 50MHz [2-3] [2-3] [1-2] [1-2]
Cyrix 166+ 133MHz 2.0x 66MHz [1-2] [2-3] [2-3] [1-2]
AMD 100MHz 1.5x 66MHz [1-2] [2-3] [1-2] [1-2]
AMD 90MHz 1.5x 60MHz [2-3] [1-2] [1-2] [1-2]
AMD 75MHz 1.5x 50MHz [2-3] [2-3] [1 -2] [1-2]
(Jumpers)
III. INSTALLATION
