Article 52183 of comp.sys.dec:

In article <33831687.190C@world.std.com> David Chase <chase@world.std.com> writes:

> Since then, I've also looked at the return address prediction claim,
> (a stack implemented in a ring of registers; hard to think of
> another way to do it if you intend to do this, and DEC has the
> patent on it) and I strongly suspect that Intel does something
> very similar to that, based on their code generation advice to
> "always pair calls and returns".

This reminds me...  When the Pentium came out there was mention of a mysterious
"Appendix H" describing Pentium scheduling rules and other optimizations, which
apparently was so hard to come by that I recall one Intel employee posting that
his copy had been stolen from his desk.

Might this secrecy have had anything to do with covering up potential patent
infringements?  AFAICS it could hardly have served to protect Intel's own
inventions, since Intel could simply have patented those for themselves.
Releasing a public Pentium optimization guide, even giving it away for free,
would then have benefited Intel at least as much as anybody else!

Example: IIRC Terje Mathisen discovered and posted some puzzling irregularities
in Pentium branch performance.  Intel might have increased their chips'
effective performance by publicizing expected irregularities in advance, no?

I also recall Andy Glew posting in this group, around the time the P6 was
announced, his "GLEW PREDICTION:" about on-chip L2 caches being a useful
compromise between L1 speed and on-chip cache mapping size.  It struck me as odd
at the time that anybody would want to predict something that had not only
already been published by DEC (eg. Tradeoffs in Two-Level On-Chip Caching by
Norman P. Jouppi and Steven J.E. Wilton, WRL research report 93/3) but moreover,
that had already made headlines in the latest Alpha.  Andy could hardly have
been unaware of it at the time, so why make a show of "predicting" it?

Maybe I'm just seeing ghosts here though.  Maybe there are good explanations for
each of these, or I'm remembering them wrong.  But they still make me curious.

I guess "you know you've been reading Usenet too long when" reading about a
topic like this suddenly reminds you of a bunch of three-year-old news
articles...  :-)


Jeroen


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