Article View: comp.arch
Article #21965Re: PUSH on i8088/i80x86
From: Craig Jackson drilex1
Date: Sat, 06 Jan 1990 16:35
Date: Sat, 06 Jan 1990 16:35
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1382 bytes
In article <182DAVISTD@MSU> DAVISTD@MSU.BITNET (Tom Davis) writes:
<In debugging some vendor code (:-) I came across what appears to be a subtle
<difference between the i8088 and i80x86. Without an i80x86 manual handy, I
<wondered if someone could verify my claim...
<
<On the i8088, a "PUSH SP" decrements SP before pushing it onto the stack. On
<the i80x86, SP is pushed onto the stack before it is decremented (somehow).
<Therefore, on the i8088 the following code does not work as expected:
<
< PUSH SP
< POP SP
<
<(SP ends up "off by two bytes".)
<-------
<Tom Davis | The above statement shall be construed,
<Network Software Services | interpreted, and governed by me alone.
<Michigan State University | EMail: davistd@ibm.cl.msu.edu
The behavior of "PUSH SP" was one of the documented differences between the
808[68] and its succcessors... this should be documented in an 80186 or
80286 manual.
--
Craig Jackson
dricejb@drilex.dri.mgh.com
{bbn,axiom,redsox,atexnet,ka3ovk}!drilex!{dricej,dricejb}
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!bbn!drilex!dricejb From: dricejb@drilex.UUCP (Craig Jackson drilex1) Newsgroups: comp.arch Subject: Re: PUSH on i8088/i80x86 Message-ID: <7296@drilex.UUCP> Date: 6 Jan 90 16:35:08 GMT References: <182DAVISTD@MSU> Organization: DRI/McGraw-Hill, Lexington, MA Lines: 25