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From: nfs@notecnirp.Princeton.EDU (Norbert Schlenker)
Newsgroups: comp.arch
Subject: Re: PUSH on i8088/i80x86
Summary: Let's finish this now - this is getting boring!
Message-ID: <22918@princeton.Princeton.EDU>
Date: 9 Jan 90 18:09:15 GMT
References: <182DAVISTD@MSU> <5524@bd.sei.cmu.edu> <10190@microsoft.UUCP> <5550@bd.sei.cmu.edu>
Sender: news@princeton.Princeton.EDU
Reply-To: nfs@notecnirp.UUCP (Norbert Schlenker)
Organization: Dept. of Computer Science, Princeton University
Lines: 48

In article <5550@bd.sei.cmu.edu| firth@sei.cmu.edu (Robert Firth) writes:
|In article <5524@bd.sei.cmu.edu>, firth@sei.cmu.edu I wrote:
|
|> Well, I just checked my manuals for the 8086, 8088, 80286 and 80386.
|> As best I can determine, all of them agree on this
|      .....
|> . There is no difference among the 80xxx processors in the semantics
|>   of the PUSH instruction
|
|In article <10190@microsoft.UUCP> gordonl@microsoft.UUCP (Gordon LETWIN) writes:
|
|>This is totally wrong.  It's a fact that the handling of "push sp" differs
|>between some of these processors.  I forget which does what and am too
|>lazy to look it up, but this is *fer sure* listed in a difference table
|>that Intel has somewhere.  And I've seen it used as part of a "identify
|>processor" subroutine.
|
|It may well, indeed, be totally wrong.  However, given that I went to
|the trouble actually to extract the documents, reread them, and post to
|the net their citations, including title, date, and order number, it
|seems to me that it would be a matter of simple courtesy, both to me
|and to the net, if you would take the same trouble before issuing a
|public contradiction.  Our opinions, even our FER SURE opinions, are
|pretty useless otherwise.

This is verbatim from Intel's 80386 Programmer's Reference Manual.
The book is Intel order number 230985-001.  Intel's number is 800-548-4725.

Section 14.7.  Differences from 8086
...
4.  Value written by PUSH SP.

    The 80386 pushes a different value on the stack for PUSH SP than the
    8086/8088.  The 80386 pushes the value of SP before SP is incremented
    as part of the push operation; the 8086/8088 pushes the value of SP
    after it is incremented.  If the value pushed is important, replace
    PUSH SP instructions with the following three instructions:

	PUSH BP
	MOV  BP, SP
	XCHG BP, [BP]

    This code functions as the 8086/8088 PUSH SP instruction on the 80386.

There are similar sections in both the 80186 and 80286 programmer's
reference manuals.  Look for "Differences" in the table of contents.

Norbert