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From: toma@tekgvs.LABS.TEK.COM (Tom Almy)
Newsgroups: comp.sys.ibm.pc
Subject: Re: V20 compatibility with Intel (Was:  Re: Is the XT dead?)
Keywords: when we get _this_ far off topic, let's change the subject line.
Message-ID: <6046@tekgvs.LABS.TEK.COM>
Date: 3 Oct 89 14:27:36 GMT
References: <25281C37.2028@maccs.dcss.mcmaster.ca>
Reply-To: toma@tekgvs.LABS.TEK.COM (Tom Almy)
Organization: Tektronix, Inc., Beaverton,  OR.
Lines: 35


This is just off the top of my head, but should be basically accurate.

8086/8088 -- "Baseline" instruction set.

80186/80188 -- Above plus 1) shifts can have constant shift counts >1,
	2) Push immediate 3) Multiply immediate 4) Push/Pop All 5) "String"
	read from/write to port (INS, OUTS instructions) 6) ENTER LEAVE and
	BOUND instructions.

V20/V30 -- Above plus some bit field instructions which I never bothered to
	learn because they only appear in V20/V30. Also 8080 emulation mode.

80286 -- Above plus protected mode.

80386 -- Above plus 80386 protected mode, virtual 8086 mode. 32 bit register
	operation optional (prefix byte) and some extra "almost orthogonal"
	addressing modes (prefix byte). Two new segment registers.
	New instructions: 1) Move with sign extension, move with zero
	extension, 2) Multiply with product in any register (but not double
	length), 3) Double register shifts and a set of bit setting and
	test instructions. 4) Set byte on condition.
	There are also some nice hardware debugging registers.

The 8018x, Vx0, and 80286 offer about the same performance levels (at the
same clock speed) which is significantly above the 808x.

As far as coprocessors, the 80287's only improvement over the 8087 is that
WAIT instructions are no longer necessary. The 80387 is significantly faster
and offers better trig function support. Again, these coprocessors are upward
compatible but not downward compatible.

Tom Almy
toma@tekgvs.labs.tek.com
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