11 Aug
2010
11 Aug
'10
9:49 a.m.
Jason Stevens scripsit:
I'll admit I'm not all that swift on the
pdp-11, but I get the impression
that the maximum exe size is 128kb with 64kb of instructions, and 64kb of
data? Isn't there something that can be done with overlays or some other
linker thing to act like an 8086/80286 with the large memory model (ie
multiple segments...?)
The PDP-11 is inherently a 16-bit-pointer machine; it has no concept
of 32-bit pointers, so it is always either in the x86 small or the x86
tiny model. On DEC's operating systems, you could indeed set up overlays
that allowed code to be swapped in and out, either to disk or to unmapped
physical memory (much quicker!) However, AFAIK ld(1) never provided that
capability to userspace, although the technique is used inside the kernel.
In any case, such tricks don't help with data space, which is strictly
limited to 64K.
--
There is / One art John Cowan <cowan(a)ccil.org>
No more / No less http://www.ccil.org/~cowan
To do / All things
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