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From: davidsen@sungod.crd.ge.com (William Davidsen)
Newsgroups: comp.sys.intel,comp.sys.ibm.pc
Subject: Re: LOADALL for 80286 & 80386
Keywords: LOADALL
Message-ID: <870@crdgw1.crd.ge.com>
Date: 19 Jun 89 19:50:58 GMT
References: <31249@conexch.UUCP>
Sender: news@crdgw1.crd.ge.com
Reply-To: davidsen@crdos1.UUCP (bill davidsen)
Followup-To: comp.sys.intel
Organization: General Electric Corp. R&D, Schenectady, NY
Lines: 29

I never cease to be amazed that some people find something which they
consider a feature in a CPU and then demand that it be documented. Back
in the CP/M days we had two sets of Z80 "secret" instructions and the
8085 "secret" instructions. This resulted in code which required an
Intel, Zilog, or Mostek CPU, and in the Mostek case, the "old" version,
since the instruction went away along with some other bugs in a later
stepping.

If Intel doesn't document it they have no need to keep it around in the
next stepping of the chip, or the 486, 586, etc. While it's fun to use
undocumented instructions, the gain in performance is seldom worth the
portability problems. 

If you write for your machine and only your machine, then use what you
want, but I can't see writing any code I would ever share which uses an
undocumented feature. What happens is that it fails on someone's
machine and they blame the software. If you write for money you don't
need unhappy customers, and if you write for fun you don't need to see
people posting flames about your work.

Maybe someone can explain how the LOADALL instruction will change my
life, other than letting me reformat my disk if it doesn't work as
(un)documented. I checked to be sure that my 386 wasn't faking it, and I
don't have a list of programs which go out with trap6.

Sounds like a solution in search of a problem to me.
	bill davidsen		(davidsen@crdos1.crd.GE.COM)
  {uunet | philabs}!crdgw1!crdos1!davidsen
"Stupidity, like virtue, is its own reward" -me