  OpenVMS Upward-Compatibility Issues? 
 The Question is:
 
Dear Sir,
 
I have an application developed on Alpha 4100
5/400 with OpenVMS 6.2 operationg system, now
I want to upgrade our system and I heard about
ES40(6/500) , Alpha 4100 5/600 and 5/533, can
I order an ES40 without modifiying our application, if not, can we order
alpha 4100 5/600 or alpha4100 5/533? Which system can run
OpenVMS 6.2 ?
 
Thanks
JInjiang Ren
July 21, 1999
 
 
 The Answer is :
 
  All systems based on the Alpha 21264 microprocessor require a minimum
  of OpenVMS Alpha V7.1-2, or potentially V7.2-1 or later.
 
  OpenVMS is expected to be upward compatible (for non-privileged-mode
  applications) for existing executables, and correct code built for
  21064 and 21164 Alpha microprocessor systems is expected to operate
  on 21265 systems.   Privileged-mode code (executive or kernel) can
  require recompilation and rebuild, or rework.  Code built with older
  compilers will not issue instructions as efficiently as code built
  with more recent tools, but will function correctly.
 
  No recompilation or rebuilding is required.
 
  Recompilation and rebuilding with more recent tools and compilers
  can improve performance.
 
  For information on one (incorrect) code construct that can cause
  problems with code executing on 21264 systems, please see the
  21264 directory on the OpenVMS Freeware V4.0 website and the
  OpenVMS Freeware V4.0 CD-ROM media.
 
  If there are latent bugs in the code, there is no way to predict the
  outcome -- please see the discussion around "Debugging synchronization
  problems? (SMP)" and "Shared memory and Alpha memory barriers (MB)?"
  here in Ask the Wizard for details on common problems and techniques
  for ensuring correct synchronization.
 
  Please see topics (3761), (5192), and (6829).
 
  Related topics include (173), (866), (1052), (1171), (1904), (2738),
  (2932), (4336), and (6049).
 
 Answer written or last revised on  11-OCT-2001 
