Motherboard Switch and Jumper Settings

To select the processor speed, there are five sets of jumpers (75 MHz, 90 MHz, 100 MHz, BF0, and BF1). When setting the processor speed, there is another jumper (PCISEL) that configures the proper PCI bus frequency.

To select the processor speed, install the jumpers as follows:

Table 1: CPU Speed Selection (* = Default configuration)

The Bus/Core Frequency Ratio jumpers (BF0 and BF1) change the way the frequency divider works. A 100 MHz processor with the 1/2 option selected will have the bus speed running at only 50 MHz. This selection is not recommended since it will degrade the bus performance, but a 120 MHz processor will require the 1/2 option selected to set the bus speed at 60 MHz. A 166 MHz processor will require the 2/5 option selected to set the bus speed at 66 MHz.

Table 2: CPU Bus Speed settings (* default setting)

The Pentium Processor family has various voltage choices depending on the CPU speed and the bin grade, they are referred to as VR and VRE. To select the proper voltage refer to the processor specification number in the documentation shipped with the processor, then follow the configuration below.

Table 3: CPU Voltage Selection

The PCISEL Jumper provides a way to select the frequency of the PCI bus. When the jumper is closed, the PCI bus frequency is 1/2 CPU clock and when the jumper is open it is 33 MHz.

Table 4: PCI Clock Jumper

The motherboard supports both Asynchronous SRAM and Synchronous Burst SRAM. A jumper must be set to specify which type is installed.

Table 5: Cache Selection