Thursday, April 4, 2013

Esoterica

I occasionally get email about things I never thought I would have to remember.  Recently, I was asked how the LMI K-machine booted.  The short answer is this:

In the K-machine schematics, in the NuBus Spy Data Paths, there is a switch near the upper right labeled AUTOBOOT.  If it is on, the machine boots from the boot prom.  Otherwise, the machine powers up in a halted state and some other device on the bus is expected to boot it externally.

Writing is hard.  My original post went into detail about we used a serial cable from an LMI Lambda to a NuBus debug card in the test rack.  You could write the K-machine memory from the NuBus to load a bootable program, then you could single step the machine through the debug path.

(Ref:  The code for the K-machine remote debugger.)

The nitty gritty details are there in the code.