Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!ucsd!usc!samsung!uunet!cbmvax!daveh
From: daveh@cbmvax.UUCP (Dave Haynie)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Shadow RAM
Message-ID: <8560@cbmvax.UUCP>
Date: 14 Nov 89 21:14:27 GMT
References: <42550@bu-cs.BU.EDU>
Distribution: comp
Organization: Commodore Technology, West Chester, PA
Lines: 19

in article <42550@bu-cs.BU.EDU>, bear@bu-pub.bu.edu (Blair M. Burtan) says:

> Does anyone think that Shadow RAM would be effective on an Ami? ...
> The claim is that RAM is faster than ROM.  Would it be possible/worth 
> the effort to take some of the graphics primitives from RAM and store them 
> in ROM?

I think you got that last part backwards.  But in any case, on a stock A500
or A2000, ROM is at least as fast as RAM.  In general, ROM is as fast as any
16 bit Fast memory.  Should you add a 68020 or 68030 CPU with 32 bit RAM,
you then get into a situation where RAM is at least four times faster than
ROM.  You also have an MMU, and thus can use the SetCPU program to copy the
entire contents of ROM into RAM, and then map that RAM to the location of the
system ROM.  This is going to affect CPU and ROM intensive operations, two of
which are layers.library and the FFP math libraries on the Amiga.
-- 
Dave Haynie Commodore-Amiga (Systems Engineering) "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy
                    Too much of everything is just enough