Frank Cox wrote:
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
I have always assumed doesemu uses the 386's virtual-8086 mode, and
that's not mentioned in Bryan J Smith's description above.
--
Cheers
John
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