Memory limits on PDP-11/70 (jfr's comments)

[utzoo!decvax!ucbvax!unix-wizards]

>From ihnss!karn at Berkeley Wed Nov 11 15:33:22 1981
I believe the addressing limit is 4 megabytes (22 bit real address).
Our '70 (ihnss) has been running with 512K of DEC core + 2 meg of
MOSTEK add-on RAM for a year or so.  We have virtually no swapping,
as you might expect, but a meg or so of memory sits virtually unused
most of the time.  It sure would be nice if we could put this to
some use, such as having more buffers, but even the buffer HEADERS
within the kernel take up too much space!

The only problem we had was that the older versions of Unix had bugs
in the memory allocation routines that would cause them to bomb when
handling addresses > 2meg.  Changing some integers to be unsigned
fixed this problem.

Phil Karn