Front Panel - Example

Example

The following procedure would bootstrap an RK05 moving-head magnetic disk on a PDP-8 system:

1. Ensure that the machine is halted by lowering and raising the Halt switch; the front panel "RUN" light should then be off.
2. Set the 12 data switches to 0030 (Octal address 30), depress the Load Address ("ADDR LOAD") switch. The address lights will change to "0030".
3. Set the switches to 6743, raise the Deposit switch. The data lights will show this instruction.
4. Set the switches to 5031, raise the Deposit switch. The data lights will show this instruction.
5. Set the switches to 0030 (Octal address 30), depress the Load Address switch. The address lights will change back to "0030".
6. Depress the Clear switch.
7. Depress the Continue switch. The "RUN" light will illuminate and the operating system on the disk will be bootstrapped.

This process works by depositing a simple, two-instruction program in memory and executing it. The first instruction commands the disk controller to begin reading the disk from the current disk address into the current memory address. The second instruction is a JMP instruction that jumps to itself endlessly. When "Clear" is pressed, the disk controller's current disk address is set to sector 0 and its current memory address is set to memory location 0000. When the read is commanded, the program stored in disk sector 0 overlays the bootstrap program and, once the JMP instruction is overlayed, the disk program takes control of the machine.