Path: utzoo!attcan!uunet!peregrine!elroy!ames!oliveb!sun!gorodish!guy
From: guy@gorodish.Sun.COM (Guy Harris)
Newsgroups: comp.arch
Subject: Re: Sw vs. Hw BitBlit.
Keywords: BitBlit.
Message-ID: <62296@sun.uucp>
Date: 1 Aug 88 20:47:44 GMT
References: <399@ma.diab.se> <1313@ucsfcca.ucsf.edu> <61783@sun.uucp> <1315@ucsfcca.ucsf.edu>
Sender: news@sun.uucp
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> (In an attempt to refute my point about substituting word-blitting
> for bit-blitting without admitting it being a debater's trick).

Excuse me, but I don't *consider* it a debating trick.  Unless you can
demonstrate that it *is* one - which you have *not* done - I have no intention
of "admitting it is (one)."

However, I *do* consider blithely dismissing arguments you don't like as
"debating tricks" to be a debating trick.

The point made by Pike and company is that the bulk of the operations performed
on the Blit *were* word-oriented, except for some that were dominated by
overhead above-and-beyond the bit-pushing, and therefore that the fact that
pushing bits on arbitrary boundaries is more expensive isn't important.

This is similar to the point that in many applications, integer multiplications
are usually multiplications by constants, and therefore machines that don't
have multiply instructions don't suffer a big performance hit in those
applications.  You *don't* always have to make the *general* case fast; you
want to concentrate on making the *common* case fast.

> Another debater's trick: this one is called Appeal to Authority.

Umm, right.  By this logic, *any* citation of *any* paper is "Apppeal to
Authority", and thus dismissable as a "debating trick".  Clever trick, that.

Sorry, but Pike and company, at least, have demonstrated some level of
expertise in the matter of making bit-mapped display hardware and software.  As
such, appealing to their authority is not without merit.

> Never mind, I suppose, that this is 3 1/2 years after publication
> of the above and who knows how long before that it was written.
> A few things have happened in this business since then.

In other words, the common types of bitblt operations have changed since then?