[TUHS] PDP-11/70 SPL (was: Early non-Unix filesystems?)

Dave Horsfall dave at horsfall.org
Mon Mar 28 05:59:43 AEST 2016

On Sun, 27 Mar 2016, Johnny Billquist wrote:

> I do not have any experience either way. I have never checked this. I'm 
> just saying that it don't make sense in my head, and the processor 
> handbook do not describe such a property of SPL. But now that I know, 
> I'm going to try and find out.

I'll say it again: it's *definitely* how SPL worked (at least, on the 
11/70 that I hung; too many witnesses...).  Somewhere Out There (tm) is a 
little self-relocating program that completely filled user memory with SPL 
(including overwriting itself; the last act it did was to overwrite 
itself, and was sheer genius).  I saw it in a ;login: newsletter, so it 
*might* be in AUUGN...  When the PC wrapped around, it was SPLs all the 
way down :-)

> It would also be interesting if anyone can come up with a good reason 
> why SPL should work that way.

Likely a firmware bug?

Dave Horsfall DTM (VK2KFU)  "Those who don't understand security will suffer."

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