[Info-vax] RealWorldTech on Poulson

[Bob Koehler]

In article <4e0e88f8$0$6590$c3e8da3$b1356c67 at news.astraweb.com>, JF Mezei <jfmezei.spamnot at vaxination.ca> writes:
> 
> Consider that a true change in architecture to really make it out of
> order, would likely require changes to all compilers and recompiling of
> software with new compilers, and it would also require that the new
> chips support the old executables with the EPIC mentality. Me thinks
> this would be way too big of a change to be acceptable.

   All the important stuff _is_ in the compilers.  Has been for decades.
   We've seen, and I wouldn't have any touble seeing more, compilers
   with chip generation knowledge.

   I was impressed just how far the DEC C compiler for Alpha would go,
   back on the first release.  I've been impressed just how much better
   some chip vendor's compilers are over gnu (I've seen perfomance
   double).

   This really shouldn't be suprizing.  Back in VAX days, Ultrix-32
   offered a choice of the standard UNIX cc, or vcc, which was based
   on the VAX C compiler for VMS.  vcc knew VAX better and the
   performance difference was real.  With RISC and VLIW it's not unusual
   to have generation specific qualifiers for compilers to generate the
   best code for different generations of the same chip.

   My only problem was not having generation qualifiers on VAX
   compilers.  All the NOPs inserted to make 6000 series systems optimal
   might not have been the right thing on my MV II.  Generating MOVCx
   certainly wasn't.