🚀 go-pugleaf

>     Joel Upchurch @ CONCURRENT Computer Corporation (A Perkin-Elmer Company)
joel@peora.UUCP writes:

>	I don't agree that applications are growing faster than
>	memory is getting cheaper. I might agree that the applications
>	are growing faster than the amount of memory usually installed
>	in most computers.
>	Back in 78 it cost me $200 dollars to add 16KB to my Apple II.
>	Last month I paid $401 to put 2 more megabytes in PC clone.

An alternate way of expressing the trend is that over the last eight years,
memory costs have halved every 1 to 2 years.  Bell's law states that
applications grow at the rate of an address bit every two to three years.
Therefore, accepting your figures as accurate, I stand corrected.  The
semiconductor industry has created ever cheaper memory products, and more
than kept up with demand, over the last eight years.  Too bad they haven't
increased the address bits of their processors at the same rate.

>	The cost of disk storage hasn't gone down nearly as fast as
>	the cost of memory. Especially the kind of high performance
>	drives that make good paging devices. You can have virtual
>	memory without fast disks, but then you need more memory
>	to maintain equivalent performance levels.

If your applications are i/o bound by paging, buy more memory.  Tuning
your application on a virtual memory machine gets you more performance
out of less memory, not adequate performance out of inadequate memory.

>	I will agree that for any given memory N, there will always
>	be applications that won't run in N. But as time goes on these
>	applications will more and more be oddballs, rather than the
>	mainstream. There will niche computers to run them, but the
>	common run of applications won't need this kind of support.

About the turn of the century, there was a serious proposal to close the
Patent Office, since everything useful had already been invented.  Let's not
limit tomorrow's application size in today's architectures.  I don't pretend
to predict tomorrow's applications.  But it's a safer bet that they'll
require more memory than to set an upper limit on typical demands.  Bell's
Law has surprising generality and longevity.

>	This is not to say that future processors won't support
>	virtual memory. Address translation/ memory protection
>	support is useful on any multitasking system, with or
>	without virtual memory and the incremental cost for
>	hardware to generate page faults isn't much. A lot
>	of people seem to be excited about the 80386, but not
>	because of virtual memory, but because of better support
>	for multitasking.

Neither.  Imagine the technical excitement of the 80386 if the IBM PC market
didn't exist, had never existed.  Yawn.  Just another pretty chip.

--> Jon Krueger
uucp: {seismo, allegra, decvax, cmcl2, topaz, harvard}!rochester!ur-tut!tuba
Phone: (716) 275-2811 work, 235-1495 home	BITNET: TUBA@UORDBV
USMAIL:  Taylor Hall, University of Rochester, Rochester NY  14627 

-- 
--> Jon Krueger
uucp: {seismo, allegra, decvax, cmcl2, topaz, harvard}!rochester!ur-tut!tuba
Phone: (716) 275-2811 work, 235-1495 home	BITNET: TUBA@UORDBV
USMAIL:  Taylor Hall, University of Rochester, Rochester NY  14627