Re: 32- versus 64-bit fedora on an AMD 64 mobile athlon?

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On Mon, 31 Dec 2007 13:16:14 -0700
Phil Meyer <pmeyer@xxxxxxxxxxxxxxxx> wrote:

> If you are having students compile stuff, then you need to stick to the 
> lowest common denominator (32bit) or else they cannot use those compiled 
> programs elsewhere.

This is a bit of a niche issue, but it may be important with regard to certain
applications.

You can use DOSEMU (http://www.dosemu.org) to run old (and new) DOS programs on
Linux.  I wrote, support and maintain what has become a fair-sized suite of
special-purpose programs for a particular industry.  For various reasons, the
programs are written in PowerBASIC/DOS and run on Linux application servers
under DOSEMU.

Linux/x86_64 runs DOS programs under DOSEMU approximately 13 times slower than
they run on Linux/i386.  This is not as big of an issue as it may initially
appear, because even 13 times slower on a 3+GHZ computer is faster than
computers were running in back in the days when DOS was king of the hill. For
an interesting description of the reason this happens, I highly recommend
this article:
http://thebs413.blogspot.com/2005/10/what-is-x86-64-long-mode-memory-model.html 

In short, running i386 Linux allows your CPU to use a “Virtual86” mode, while
x86_64 Linux requires that the whole thing be emulated in software which
obviously takes more horsepower and therefore runs more slowly

My conclusion is that if you want to run the occasional DOS program on Linux,
then x86_64 may be worth using depending on what other native Linux programs
you normally use and require. On the other hand, if you are setting up a server
for the main purpose of running DOS programs on it (like I do) then i386
(32-bit) Linux is the way to go, simply because a 13 times increase in speed is
obviously worth having.


-- 
MELVILLE THEATRE ~ Melville Sask ~ http://www.melvilletheatre.com


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