RK05/RL02 Boot Sequence

From: Paul Koning <pkoning_at_equallogic.com>
Date: Thu Jul 1 08:56:42 2004

>>>>> "wai-sun" == wai-sun chia <squidster_at_techie.com> writes:

 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
Received on Thu Jul 01 2004 - 08:56:42 BST