UNIXpc per-process VM limit (Was: Re: Swapping and wmgr)

[Ford Prefect]

In article <365 at manta.UUCP> brant at manta.UUCP (Brant Cheikes) writes:
>In article <3030 at crash.cts.com> ford at crash.CTS.COM (Michael Ditto) writes:
>>The Unix PC supports 4M of virtual memory PER PROCESS, with a total amount
>>dependant on your physical memory + swap space.
>
>I would like to see this claim substantiated.  On page 2-1 of the AT&T
>UNIXpc Interface Specification ("Detailed Interface Specification")
>for version 3.51, it says:
>
>	"Minimum real memory is 512K [...] and maximum process
>	size for a virtual memory program is 2.5 megabytes."
>
>Who's correct, the FM or Mr. Ditto?

The manual is more accurate than I was.  What I meant to say was that
the Unix PC has 4 megabytes of virtual address space per process.
2.5M of that is usable for what most of us think of as "program"
memory.  The rest is shared library, shared memory, and reserved
kernel space (bogus design tradeoff).

What I mean by 4 megabytes of virtual address space is that the bottom
22 address lines (including the imaginary A0) coming off the CPU are
decoded for user programs and converted into a physical memory
location.  Actually, all 24 address bits are decoded, but only the
kernel is allowed to set the top two.

					-=] Ford [=-

"Once there were parking lots,		(In Real Life:  Mike Ditto)
now it's a peaceful oasis.		ford%kenobi at crash.CTS.COM
This was a Pizza Hut,			...!sdcsvax!crash!kenobi!ford
now it's all covered with daisies." -- Talking Heads