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16 ASUS P5A User’s Manual
III. INSTALLATION
Jumpers
III. INST ALLATION
5. CPU External (BUS) Frequency Selection (FS3, FS2, FS1, FS0)
These jumpers tell the clock generator what frequency to send to the CPU, chipset,
and AGP. 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 fre-
quency (the advertised CPU speed).
6. CPU to BUS Frequency Multiple (BF0, BF1, BF2)
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 in conjunction with the jumpers for CPU External (BUS) Frequency Selection.
Match the Mult. (Multiple) column of
the table on the opposite page to these
CPU types:
P5A
R
CPU External Clock (BUS) Frequency Selection
95MHz
63.3MHz
31.6MHz
1
2
3
100MHz
66.6MHz
33.3MHz
105MHz
70MHz
35MHz
CPU
AGP
PCI
→
→
→
60MHz
60MHz
30MHz
1
2
3
66.8MHz
66.8MHz
33.4MHz
75MHz
75MHz
37.5MHz
75MHz
60MHz
30MHz
83.3MHz
66.6MHz
33.3MHz
CPU
AGP
PCI
→
→
→
FS3
FS2
FS1
FS0
FS3
FS2
FS1
FS0
FS3
FS2
FS1
FS0
FS3
FS2
FS1
FS0
115MHz
77.6MHz
38.3MHz
1
2
3
120MHz
80MHz
40MHz
CPU
AGP
PCI
→
→
→
110MHz
73MHz
36.6MHz
CPU A: AMD-K6-III, AMD-K6-2/400&faster
CPU B: AMD-K6-2/380&slower, AMD-K6
CPU C: Intel Pentium P54C, AMD-K5
CPU D: Intel Pentium P55C, IBM/Cyrix
6x86MX, IBM/Cyrix M II
CPU E: IBM/Cyrix 6x86, IBM/Cyrix 6x86L
CPU F: IDT WinChip 2™
CPU : BUS Frequency Multiple
CPU A
CPU B
CPU C
CPU D
CPU E
CPU F
4.0x(4/1)
4.0x(4/1)
—
—
—
4.0x(4/1)
4.5x(9/2)
4.5x(9/2)
—
—
—
4.5x(9/2)
BF0
BF1
BF2
→
→
→
→
→
→
5.0x(5/1)
5.0x(5/1)
—
—
—
2.33x(7/3)
5.5x(11/2)
5.5x(11/2)
—
—
—
2.66x(8/3)
BF0
BF1
BF2
BF0
BF1
BF2
BF0
BF1
BF2
3.0x(3/1)
3.0x(3/1)
3.0x(3/1)
3.0x(3/1)
—
3.0x(3/1)
2.5x(5/2)
2.5x(5/2)
2.5x(5/2)
2.5x(5/2)
1.0x(1/1)
2.5x(5/2)
6.0x(6/1)
2.0x(2/1)
2.0x(2/1)
2.0x(2/1)
2.0x(2/1)
3.33x(10/3)
3.5x(7/2)
3.5x(7/2)
1.5x(3/2)
3.5x(7/2)
3.0x(3/1)
3.5x(7/2)
CPU A
CPU B
CPU C
CPU D
CPU E
CPU F
→
→
→
→
→
→
1
2
3
BF0
BF1
BF2
BF0
BF1
BF2
BF0
BF1
BF2
BF0
BF1
BF2
1
2
3
WARNING! Frequencies above 100MHz exceed the specifications for the on-
board chipset and are not guaranteed to be stable. The table on the following
page is for general reference purposes only. Always refer to the instructions in-
cluded with your CPU when possible.