Understanding The Different Clock Speeds - TYAN TOMCAT IVS D Manual

3.13 Understanding The Different Clock Speeds

The following chart shows the different CPU, mainboard and PCI fre-
quencies. As you may have noticed, all the Intel Pentium CPUs use an
internal clock multiplier(x3, x2.5, x2 or x1.5 Motherboard speed). All
Cyrix 6x86 can only use a x2 clock mulitipplier.
Pentium
Internal Clock
75 MHz
90 MHz
100 MHz
120 MHz
133 MHz
150 MHz
166 MHz
200 MHz
In the table above, the 50, 60 and 66.67 MHz figures are oscillator speeds
that establish the external clock speed. The PCI Bus clock speed is fixed at
one half of the mainboard clock speed. The 150MHz Pentium when set for
2.5x mode will achieve a 30MHz PCI bus speed but if it is set for 3x mode
you will get a slower 25MHz PCI bus speed.
Since all of the Cyrix 6x86 CPU's use a x2 mulitplier, the 100MHz P120+
must run on a 50MHz host bus. The PCI speed will then be at 25MHz.
S1564-001-01 www.tyan.com
Mainboard
Clock
50 MHz
60 MHz
66.67 MHz
60 MHz
66.67MHz
60 MHz
66.67 MHz
66.67 MHz
19
PCI Bus
Clock
25 MHz
30 MHz
33 MHz
30 MHz
33 MHz
30 MHz
33 MHz
33 MHz