Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!purdue!haven!vrdxhq!daitc!daitc.daitc.mil
From: jkrueger@daitc.daitc.mil (Jonathan Krueger)
Newsgroups: comp.arch
Subject: Re: RISC and emulated languages
Message-ID: <513@daitc.daitc.mil>
Date: 9 May 89 18:48:51 GMT
References: <158@bms-at.UUCP>
Sender: jkrueger@daitc.daitc.mil
Reply-To: jkrueger@daitc.daitc.mil (Jonathan Krueger)
Organization: DTIC Special Projects Office (DTIC-SPO), Alexandria VA
Lines: 32

In article <158@bms-at.UUCP>, stuart@bms-at (Stuart Gathman) writes:
>There is one interesting feature of RISC architecture that I haven't seen
>mentioned much: the fact that an emulated/interpreted program will often
>run faster than a compiled one.
>...
>This approach turns a RISC machine into a CISC machine with user defined
>microcode.  Unlike loadable microcodes of yesteryear, the cache is swapped
>by line on a demand basis.

One might also cite relational engines for DBMS, which interpret query
languages (even when executing "compiled" procedures, they do not
generate standalone images, they just pre-fetch and "decode" (parse
and optimize) the query.  Clearly this approach yields a more flexible
system than linking (ISAM, VSAM, etc.) routines into each image.  The
surprising part is it can be faster, too.  One reason is that the
engine can do a better job of staying in cache than the images.  The
engine implements common functions that service everyone.  The most
often used ones are found in cache.  (Sets of images lose even when
the operating system supports execution from shared memory, because
it's hard to decide at runtime whether each image's routines can
service other images.)  And unlike loadable microcodes of yesteryear,
they allocate fast memory in response to usage patterns that vary at
runtime.

So next time you get a new release of your RDBMS, just tell management
that you're installing new microcode :-)

-- Jon

Jonathan Krueger 
...uunet!daitc!jkrueger     jkrueger@daitc.mil     (703) 998-4600
		My opinions are not necessarily those of my wallpaper.