[TUHS] Bootstrapping UNIX - how was it done

[John Levine via TUHS]

It appears that Peter Weinberger (温�  � �) via TUHS <pjw at google.com> said:
>As I remember, the 11/70 was booted just as John describes. One keyed
>in a boot loader at the console.

I'm pretty sure our PDP-11 at Yale had a boot ROM, so you just set
the starting address from the switches and started it.

Before that I toggled boot loaders into PDP-8's and I don't miss it.

R's,
John


>
>On Mon, Mar 23, 2026 at 3:11 AM John P. Linderman via TUHS
><tuhs at tuhs.org> wrote:
>>
>> >
>> > >How was UNIX bootstrapped in the early days?
>> >
>> > When I started at the Labs in 1973, what eventually morphed into the
>> Programmer's Workbench UNIX ran a PDP45 in Piscataway, NJ. UNIX was
>> sufficiently flakey at that time that they liked to reboot the system each
>> day to clean up corruption in the file system. Someone noticed that I
>> arrived before 6 am every morning, when a reboot would go unnoticed by most
>> people. So I was taught how to halt the system, set a bunch of keys on the
>> front of the 45, and hit start. I'm guessing that the keys simply directed
>> the 45 to read a boot block from some device, and execute the instructions
>> in that block, where the real software bootstrapping began. I'm sure others
>> in this group can supply the correct details. I was not then, and still am
>> not now, a hardware person, but I remain an early riser. -- jpl
>