Compaq AlphaPC 164SX Switch Configuration, Mini-Debugger CF3, CPU Speed Selection CF64

3

AlphaPC 164SX Switch Configuration

The AlphaPC 164SX motherboard has a switchpack located at SW1, as shown previously in Figure 2–1.These switches set the hardware configuration. Figure 3–1shows these switch configurations.

3.1 Mini-Debugger (CF3)

The Alpha SROM Mini-Debugger is stored in the flash ROM and is enabled/ disabled by switch CF3. The default position for this switch is on (see Figure 3–1). When this switch is off, it causes the SROM initialization to trap to the Mini- Debugger after all initialization is complete, but before starting the execution of the system flash ROM code.

3.2 CPU Speed Selection (CF[6:4])

The clock synthesizer at U45 makes it possible to change the frequency of the microprocessor’s clock output. The switch configuration is set in SW1, CF[6:4]. These three switches set the speed at power-up as listed in Figure 3–1.The microprocessor frequency divided by the ratio determines the system clock frequency.

3.3 Fail-Safe Booter (CF7)

The fail-safe booter provides an emergency recovery mechanism when the primary firmware image contained in flash memory has been corrupted. When flash memory has been corrupted, and no image can be loaded safely from the flash, you can run the fail-safe booter and boot another image from a diskette that is capable of repro- gramming the flash.

Refer to Section 8.4 for more information.

AlphaPC 164SX Switch Configuration 3–1