Path: utzoo!attcan!uunet!wuarchive!julius.cs.uiuc.edu!apple!altos!altos86!rcollins
From: rcollins@altos86.Altos.COM (Robert Collins)
Newsgroups: comp.sys.ibm.pc.misc
Subject: Re: Difference between a 386 and a 386sx
Keywords: 386 386sx
Message-ID: <4088@altos86.Altos.COM>
Date: 19 Sep 90 15:47:29 GMT
References: <1990Sep16.194605.11968@ecn.purdue.edu> <4383@bwdls58.UUCP> <14110@mentor.cc.purdue.edu>
Reply-To: rcollins@altos86.UUCP (Robert Collins)
Organization: Altos Computer Systems, San Jose, CA
Lines: 24

In article <14110@mentor.cc.purdue.edu> edgincd2@mentor.cc.purdue.edu (Chris Edgington *Computer Science Major*) writes:
>If you wanted to determine whether or not the chip you are using is a 386
>or a 386sx, couldn't you just execute some 32 bit intructions and time the
>number of machine cycles it takes to execute them.
>
I think what you mean to say is to execute some bus-bound instructions, 
and time the execution.  If you have a purely CPU-bound instruction, like
BSF EAX, ESI, then the execution time is the same on SX and DX, given
the same clock speeds, regardless of the fact that this is a 32-bit
instruction.
 
So, to answer the question I think you were asking:
No.  Many early 386 machines were implemented using a 286-designed
motherboard.  Therefore, these machines had 16-bit buses.  But regardless
of this fact, some buses run at 8Mhz, some at 8.33Mhz, some at 10Mhz,
and others at 11Mhz.  So, this would hardly be a fail safe way to tell
the SX from DX.

 
-- 
"Worship the Lord your God, and serve him only."  Mat. 4:10
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