[TUHS] Bootstrapping UNIX - how was it done

[Warner Losh via TUHS]

On Thu, Mar 26, 2026, 5:29 AM bruner--- via TUHS <tuhs at tuhs.org> wrote:

> Most of the PDP-11's I used had boot ROMs, but I do recall at least one
> machine where the boot procedure was
>
> Set HALT/RUN to HALT
> Press START
> LOAD ADDR 777404
> DEP 5
> LOAD ADDR 0
> Set HALT/RUN to RUN
> Press START
>
> The reset cleared all of the controller registers, so this read 64Kwords
> from RK05 drive 0 into memory starting at 0. A little overkill for reading
> one 512-byte block...
>

Boot time was optimized in favor of the operator key in time over the time
to read in blocks from the disk...

Warnet

--John
>