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From: barmar@think.com (Barry Margolin)
Newsgroups: comp.arch
Subject: Re: RISC hard to program?
Message-ID: <40767@think.Think.COM>
Date: 17 Jul 90 22:39:23 GMT
References: <2162@opus.cs.mcgill.ca> <3648@auspex.auspex.com> <2163@opus.cs.mcgill.ca>
Sender: news@Think.COM
Organization: Thinking Machines Corporation, Cambridge MA, USA
Lines: 41

In article <2163@opus.cs.mcgill.ca> peterd@opus.cs.mcgill.ca (Peter Deutsch) writes:
>Of course, the benefits of such compromises may outweigh
>the costs (as seems to be the case in SPARC) but they
>certainly don't qualify for my rigid definition of a
>feature (ie if I was offered the identical machine, but
>without the "feature" would I be more inclined or less
>inclined to buy the machine?). 

I generally refer to features that I don't like as "misfeatures".  A "bug"
is when the system doesn't conform to the vendor's description.  A
misfeature is when it does conform, but the vendor's description doesn't
describe a system that behaves as I'd prefer.  Sometimes a misfeature is
due to a design choice (e.g. making aligned memory accesses faster at the
expense of unaligned accesses); other times it's simply the lack of a
feature that a user would like (e.g. a COMPILE-ALGOL-IMMEDIATE
instruction).

>I know I'm bucking an entire industry trend here, as RISC
>seems to have been a huge commercial success, but this
>argument strikes me as suspiciously like that of a car
>salesman who argues that if I'm willing to buy a car
>without brakes or seatbelts, I can get one that is that
>much faster or cheaper. Sure, but I _am_ getting less car.

It frequently depends on the application whether this is a feature or
misfeature.  Most people wouldn't buy a bicycle without brakes or multiple
speeds.  But racing bicycles have neither.  It's not a matter of "less
bicycle", but merely that the bicycle is optimized for speed rather than
user-friendliness.

Or, returning to your car analogy, what if it were the emission control
system rather than the brakes or seatbelts that were being proposed for
removal.  An environmentalist would consider this a misfeature, while a
performance enthusiast would consider it a feature.  Tradeoffs frequently
have to be made, and whether the chosen path is best depends on your
perspective.
--
Barry Margolin, Thinking Machines Corp.

barmar@think.com
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