why different swapping modes on executables?

[thomas at nexus.se]

In article <573 at adpplz.UUCP> martin at adpplz.UUCP (Martin Golding) writes:
<text deleted>

   My impression is that the (original) version of the Magic Number was
   the actual value to load into the PDP 11 MMU control register, to select
   one or the other model.

Actually the magic numbers for the PDP11 was a branch instruction that
made the processor jump past the header. Writeable text (code was trated as
data) had 0407 which meant jump 7 words forward and read/execute-only text
had 0410 which meant jump 8 words (the magic numbers were in octal) forward.

I don't know whether the magic number actually WAS executed, it sure could
have been.

There was also a 0411 which was separate I and D spaces.
Pageable objects have 0413, don't know if this was ever used on a pdp11.

Thomas

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