Newsgroups: comp.sys.ibm.pc.hardware
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!magnus.acs.ohio-state.edu!csn!kessner!david
From: david@kessner.denver.co.us (David Kessner)
Subject: Re: Why buy a DX over an SX?
Message-ID: <1991Apr9.235733.11567@kessner.denver.co.us>
Organization: Kessner, Inc.
References: <14534@encore.Encore.COM>
Date: Tue, 9 Apr 91 23:57:33 GMT


There is a common misconception that 386's are faster than 286's, and that
486's are a lot faster than 386's, etc, etc, etc...

When running MS-DOS software the 286, 386sx, and 386DX are all about the
same speed (for the same clock speed).  Cached machines will generally
outperform non-cached machines (by 20-30% in 25mhz machines).

So why even bother with a 386sx-- why not stick with the 286?  Here is
the story...

If only MS-DOS software is used, a 286 is the best choice.

A 386sx will give you better memory managment, as well as multitasking and
enhanced-386 in Windows.  It will run normal 386 software, but slower than 
a 386DX.

A 386DX is a good chioce because they dont make a 25mhz and 33mhz SX.  It
will also run 386 software signifigantly faster than an SX at the same 
clock speed.

A 486 will give you floating point performance, and about 30-50% faster 
overall when compared to a DX of equal clock speed.


So.  If all you are going to do is run Windows, and you can live with 16-20mhz
CPU's, then an SX is perfect.

If you are thinking that this performance curve (286=386sx=386dx) is all wrong
then you are right!  It's not that the CPU's are wrong, but that MS-DOS is
wrong-- since it places signifigant limitations on the program running.
On the average, a program that is re-compiled to run in 386-protected mode
will run twice as fast on the same machine!

Running 386-protected mode software, the line-up is more like:
	A 386dx is two-three times faster than an equivalent 286 program.
	386sx is about  30-40% slower than a 386dx.
	a 486 is TWICE as fast as a 386dx, 3-4 times faster in floating point.

The bottom line is that is PERFORMANCE is what you want-- then MS-DOS should
not be on your wish list.

-- 
David Kessner - david@kessner.denver.co.us            | do {
1135 Fairfax, Denver CO  80220  (303) 377-1801 (p.m.) |    . . .
If you cant flame MS-DOS, who can you flame?          |    } while( jones);
