🚀 go-pugleaf

In article <593@gp.govt.nz> don@gp.govt.nz (Don Stokes, GPO) writes:
>In article <6808@pt.cs.cmu.edu>, lindsay@MATHOM.GANDALF.CS.CMU.EDU
(Donald Lindsay) writes:
>> My trusty VAX Architecture Handbook states that a process may have at
>> most 2 GB of virtual memory.
>
>Of course that is 2GB *virtual*.  
>
>But my VAX/VMS internals manual gives the page table entry's page frame 
>number size as 21 bits = 2^21(pfn) * 512(page size) = 1GB.

	As sometimes occurs, both are correct.  The VAX architecture features
a split instruction and data space, and there are page tables for each of the
spaces.  1 GB of instruction space + 1 GB of data space = 2 GB of virtual
address space.
	This is not to mention the other bit (of course) that indicates that
you are accessing the 2 GB of virtual space reserved for the system, where
all the real interesting stuff is -- the real memory, the i/o devices and
the page tables themselves.
-- 
Gregory G. Woodbury
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