Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83; site mmintl.UUCP
Path: utzoo!linus!philabs!pwa-b!mmintl!franka
From: franka@mmintl.UUCP (Frank Adams)
Newsgroups: net.arch
Subject: Re: Page size and the meaning of life
Message-ID: <735@mmintl.UUCP>
Date: Fri, 25-Oct-85 17:13:58 EST
Article-I.D.: mmintl.735
Posted: Fri Oct 25 17:13:58 1985
Date-Received: Thu, 31-Oct-85 04:06:32 EST
References: <926@decwrl.UUCP> <931@lll-crg.ARpA> <146@opus.UUCP>
Reply-To: franka@mmintl.UUCP (Frank Adams)
Organization: Multimate International, E. Hartford, CT
Lines: 25
Summary: It depends on the application(s)


In article <146@opus.UUCP> rcd@opus.UUCP (Dick Dunn) writes:
>> Would anyone care to comment on why we need virtual memory at all
>> with a 256 meg real memory being available in the near future?
>
>Second response:  VM is a means for getting more use out of the memory
>you've got.  Until that 256 Mb is almost free, there's a cost tradeoff to
>be considered for how much memory you put in.  VM sets the "hard limit" of
>a process address space independently of the actual physical memory on the
>machine, so you don't have to go out and buy more memory to run a program
>with a large address space--it just runs slower.  (Yes, in some cases it
>runs intolerably slower.  If that happens, go buy more memory, obviously.)

What leads either of you to believe that 256M will be enough to run your
programs?  Memory used by programs expands to use the space available.
There was a time, not so long ago, when 256K was a lot of memory, and
people didn't understand how any program could use more than 16M.  If
memory becomes sufficiently cheap, there are time/space tradeoffs which
can be made to use large blocks of it.

Or, for a second response, if memory becomes cheap enough, what do you
need *disks* for?  You will need a hardware solution to preserve memory
in the event of system/power crashes, of course.

Frank Adams                           ihpn4!philabs!pwa-b!mmintl!franka
Multimate International    52 Oakland Ave North    E. Hartford, CT 06108