The CPU Daughter Card contains two switch packs, both shown on the CPU Daughter Card - Top:
- The CPU speed switches
- The PLL divisor switches
Note: System owners should not arbitrarily change the settings on either of these switch packs; they are for the use of authorized service and maintenance providers only.
CPU Speed Switches
The CPU speed switches are set to the appropriate speed for the CPU in your system. They are not used to change or upgrade the speed of your system, only to interface with the CPU chip onboard at the present time. The following example illustrates the switches set at 500 MHz (switches 1-4 on, off, off, and on, respectively). If you have a 667 MHz Compaq AlphaStation XP1000, refer to the table for the proper switch settings.
Speed
(MHz) | System
Clock | PCI
Clock | Switch 1 | Switch 2 | Switch 3 | Switch 4 |
| 500 | 83 | 33 | On | Off | Off | On |
| 667 | 83 | 33 | Off | Off | Off | On |
Note: All other CPU switch combinations are reserved for future use.
PLL Divisor Switches
This switch pack sets the remaining divisor inputs to the MPC12439 PLL, the root of all clocks on the CPU Daughter Card. It multiplies/divides a 16.6667 MHz clock based on the M6:0 and the N1:0 values applied to it.
The following example shows the switches set appropriately for the Compaq AlphaStation XP1000 System.
A TIG reset switchpack on the MLB is used to configure the Tsunami Chipset during system reset. For the exact location of the switchpack on the MLB, see MLB Components.
Note: These switches should not be moved from the position indicated for your system; they are displayed here only as a check while troubleshooting (to see if they have been moved).
The following example illustrates the switches set for the 667 MHz Compaq AlphaStation XP1000 (switches 1-8 off, on, off, off, on, off, on, and off, respectively). If you have a 500 MHz Compaq AlphaStation XP1000, refer to the table for the proper switch settings.
Speed
(MHz) | Switch 1 | Switch 2 | Switch 3 | Switch 4 | Switch 5 | Switch 6 | Switch 7 | Switch 8 |
| 500 | Off | On | Off | Off | On | Off | Off | Off |
| 667 | Off | On | Off | Off | On | Off | On | Off |
