Programs compiled under xenix run slower under unix?

[Roger Knopf 5502]

In article <57 at dynasys.UUCP> jessea at dynasys.UUCP (Jesse W. Asher) writes:
>I was wondering if programs compiled under unix and then moved to
>a unix system would run slower than if they had been compiled
>under the unix system.  I'm not asking if a program will run
>slower or faster on a unix or xenix system.  What I'm asking really
>is "Does the process of translating xenix programs on a unix system
>slow the program down?"  I was going to give someone a program I 
>had compiled on a xenix system, but he refused it saying that he
>wanted to compile it on his system (unix) because the program
>would run slower.  It this true?  Thanx in advance.

There is nothing inherent in a Xenix (x.out) 386 binary that would cause
it to run slower under SCO Unix.

The common assumption stated above, that Xenix programs are "translated"
to run under SCO Unix, is absolutely incorrect for 386 programs. SCO went 
to a lot of trouble to put true native execution of Xenix binaries in SCO 
Unix.  There is no translation or emulation. Full support is there, just
like it was in Xenix.

286 binaries need translation for system calls under SCO Unix. Xenix 386
handled system calls from 286 binaries directly in the kernel, but when 
SCO Unix execs a 286 binary, /bin/i286emul is invoked to run the program.  
If the program in question does a lot of system calls, it may be slower than 
under Xenix. If the program is medium or large model 286, system call 
translation is not nearly as much of an issue as having 286 
code - recompiling as 386 would make it faster, but not necessarily 
because of translation. This is less true for small model programs.

Roger Knopf
SCO Consulting Services
rogerk at sco.com  or  {uunet,sun}!sco!rogerk