Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!batcomputer!riley
From: riley@batcomputer.tn.cornell.edu (Daniel S. Riley)
Newsgroups: comp.sys.amiga
Subject: Re: Denise/Paula/Agnus/Gary/Portia
Message-ID: <8566@batcomputer.tn.cornell.edu>
Date: 6 Aug 89 14:58:10 GMT
References: <1388@bnr-fos.UUCP> <713@neptune.UUCP>
Reply-To: riley@tcgould.tn.cornell.edu (Daniel S. Riley)
Organization: Cornell Theory Center, Cornell University, Ithaca NY
Lines: 47

In article <713@neptune.UUCP> esker@neptune.UUCP (Lawrence Esker) writes:
>In article <1388@bnr-fos.UUCP> protcoop@leibniz.uucp () writes:
>>that the Amiga 3000 did not use Commodore's custom chips but used some
>>'off the line' parts by other companies, for example the TI 34000 (?)
>>blitter.  Let us further suppose that all of the system software looks
>>the same to the programmer, i.e. all of the function calls are the same.
>>Would it not be possible for current software to work on both the new
>>hardware and the old hardware?

>In the land of dragons, unicorns and faeries, you are absolutely correct
>in your assumptions.  From what I've seen in the Amiga and from Comodore
>in the last 4 years, what you suggest is why Comodore stresses the proper
>use of library routines, etc.  But, a big but, there are alot of developers
>out there who, for whatever reasons, beleive they can get squeeze better
>performance out of the machine by doing things their own way.  Look at how
>much software breaks when there have been operating system changes.  EVERY
>ONE OF THESE FAILURES IS DUE TO VIOLATING AMIGA "RULES", imho.

Not every feature of the machine is available in a hardware independent
fashion.  Sometimes, a programmer really needs to build a custom COPPER
list, or directly manipulate the blitter registers.  There are *legal* 
system supported ways to do these things which are manifestly not hardware
independent, and which would break if an "Amiga" were built with
off-the-shelf parts instead of the custom ICs.  Clearly it's better to
use the system supplied routines whenever possible, but it just isn't
always possible, and not just for games.  Your typical spreadsheet or
wordprocessor should work on such an "Amiga", but some high-performance
graphics applications certainly wouldn't without some rewriting.  This
should become less common as more powerful CPUs become more common, since
the blitter has a much smaller speed advantage over a '20 or '30 with a
fast clock (as long as the manipulations can be done in 32-bit ram, and are
complex enough to justify copying in and out of chip ram).

>By the way, you touched on THE reason the Amiga is superior to all other
>computer systems on the market, including UNIX and VAX machines.  The common
>programmers interface that operates every feature of the machine in a
>unilateral and upward compatible means.

Both Unix and VMS have standard programmer interfaces.  They couldn't work
otherwise--especially UNIX, which runs on a wide variety of very different
architectures (where VMS only runs on variations on the same basic VAX).
In fact, VMS and UNIX are better because memory protection forces you to
use the standard interface--you can't twiddle the bits in the hardware
registers without shifting to a priveleged processor mode.

-Dan Riley (riley@tcgould.tn.cornell.edu, cornell!batcomputer!riley)
-Wilson Lab, Cornell U.