PDP OS Boot Sequence: WAS Re: RK05/RL02 Boot Sequence

wai-sun> Hello list, I'm trying to figure out the boot sequence on wai-sun> both the RK05 and RL02 drive from a PDP. Here's how I wai-sun> understand it so far: wai-sun> 1. Get the bootstrap in core either via the FP or PTR. wai-sun> 2. Execute bootstrap and pull in the absolute loader from wai-sun> 1st. sector of 512 bytes or 256 words; i.e. copy 1st. sector wai-sun> of drive to core starting from 0 3. Execute absolute loader wai-sun> by a JMP 0. 4. ??? What happens next ??? Typically, what happens next is that more initialization code is read in from the disk. How much and where it comes from depends on the OS. For example, in RT11 the bootstrap is 2 blocks long (block 2 is the rest). It reads the directory to find the kernel and loads that, then jumps to it. (Give or take some handwaving; Megan can improve on this in her sleep...) In RSTS, the bootstrap contains a list of disk blocks where the init.sys program lives; first it moves itself up into high memory and then it reads init.sys using that table, and jumps to the entry point. Init.sys finds all the hardware, does all sorts of setup, and finally loads the OS. IAS and RSX-11D have a saved memory image; the boot loader loads that and then fakes a powerfail interrupt. The power restore routines then reinitialize ths OS and drivers, and you're up. Other PDP11 operating systems -- no idea, but changes are it's a variation on one of these themes. paul