Date: Fri, 5 Feb 93 12:34:43 EST
From: eichin AT tweedledumber ("Mark W. Eichin")
To: IMHW400 AT INDYVAX DOT IUPUI DOT EDU
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: re: Help on 80387 emulator

>> From: "Mark H. Wood" <IMHW400 AT INDYVAX DOT IUPUI DOT EDU>
>>   o	A 486 DX is a complete chip.

True. (Intel is allegedly going to stop shipping these soon, replacing
them with one of the new low-power chips, but programmers certainly
won't notice the difference.)

>>   o	A 486 SX is a complete chip but with the FPU "disabled".  I suppose
>>   that they just erased a couple of critical traces on one of the masks.
>>   Unlike the 386 SX, it has full-width external address and data buses.

This was *once* true; now the 486SX is a distinct die, and is much
cheaper to produce (the FPU has a lot of transistors on it; leaving
out means a smaller die which means a higher yield.)

>>   o	A 487 "coprocessor" is a 486 DX that knows how to disable your 486 SX
>>	   completely and take over its work.
>>   It sounds just crazy enough to be true.

This is still true. There exist motherboards that will take a 487
*without* a 486SX. Isn't clear that this saved you anything since the
motherboard in question wasn't that cheap.
	There have been articles all over the net and the trade rags
on all of this. Don't believe me if you don't have to :-)
							_Mark_