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Path: utzoo!utgpu!water!watmath!clyde!rutgers!seismo!rochester!ritcv!cci632!rb
From: rb@cci632.UUCP
Newsgroups: comp.arch
Subject: Re: 64 Vs 32
Message-ID: <1170@cci632.UUCP>
Date: Thu, 30-Apr-87 18:41:25 EDT
Article-I.D.: cci632.1170
Posted: Thu Apr 30 18:41:25 1987
Date-Received: Sat, 2-May-87 01:31:48 EDT
References: <3810013@nucsrl.UUCP> <28200016@ccvaxa> <1316@ames.UUCP> <1071@osiris.UUCP>
Reply-To: rb@ccird2.UUCP (Rex B)
Organization: CCI, Communications Systems Division, Rochester, NY
Lines: 35
Keywords: address size, physical memory limits, RAM disks

In article <1071@osiris.UUCP> phil@osiris.UUCP (Philip Kos) writes:
>In article <1316@ames.UUCP>, lamaster@pioneer.arpa (Hugh LaMaster) writes:
>>   If a 1 MIP system a few years ago needed 16MBytes of virtual
>> and 4 MBytes of physical memory (my own figures), a 100MIP system needs about
>> 2GB of virtual and 512 MBytes of physical memory....

>That's assuming that MIPS and physical/virtual memory scale linearly.  I
>have my doubts about this.

>While MIPS (for the sake of argument, let's use the "wise man's definition",
>or "Meaningless Index of Processor Speed") and virtual memory size may have
>a more or less linear interrelationship, I've noticed more of a logarithmic
>relationship between virtual and real memory.

>Am I the only person out here who doesn't agree?

There is actually a possibility that as speed increases, memory requirements
might even go down.

It mostly depends on what the processor is being used for.  If the purpose
for using the higher speed processor is to service more users on relatively
dumb terminals, there is a good chance that replacing an 8 mips machine
with an 80 mips machine and going from 20 users to 200 user would result
in requirements for more memory and disk space.

On the flip side, if one is simply placing the faster processor into an
"intelligent terminal" or one that is primarily involved with manipulating
bit maps, there is a good chance that the 10 fold increase in speed would
not necessarily imply a 10 fold increase in memory requirements.

There are some applications such as special purpose communications, where
the additional processing speed can be very important, yet the actual
memory requirements change very little.

Rex B.