With the advent of 64bit architecture from AMD and Intel, there has been an occasional post here and there on the effects on BJ simulators. As these posts have displayed a lack of understanding of computer architecture; I thought I would put together a few words on the subject and talk to CV futures.
    [*]Performance - First, it is important to understand that 64bit architecture refers to the ability of a PC to directly address more memory than 32bit architecture. This has nothing to do with a computer?s arithmetic units or word size. (It does normally refer also to the size of some internal registers.) 64bit architecture can improve the performance of large servers, large databases and certain extremely heavy graphics applications. There are also some improvements to security and minor performance improvements in accessing system functions. However, 64bit architecture, in and of itself, will not significantly affect the performance of the vast majority of applications. There is no reason to believe that BJ simulations will be affected by the change to 64bit addressing, particularly since BJ sims make relatively little use of system services. Performance of most applications will be affected by other architectural differences that are implemented on these chips. Some of these changes will help and some will hurt. The overall effect will require benchmarks specific to the simulator.[*]Accuracy - The accuracy of BJ simulators will not be affected by a move to 64bit architecture. (Unless the simulator is poorly written and changed to make use of new features.) CVData/CVCX already make use of 64bit calculations where necessary.[*]Random Number Generation - First, 32bit RNG?s will work under 64bit architecture without modification. Again, 64bit architecture does not refer to arithmetic. (Even if it did refer to the addition of 64bit arithmetic, 32bit RNG?s would still function correctly.) Secondly, I don't feel comfortable with 32bit RNG's anyhow. It is true that most BJ simulators use 32bit RNG?s. However, CVData/CVCX has used 64bit random number generation since the first release. And I believe Cacarulo?s and James Grosjean?s simulations also use 64bits.[/list]

    Given the above, no changes are planned for CV software as a results of 64bit chips. There simply is no reason. Performance is an unknown. The 64bit chips have slower cycle times. This by itself reduces performance. But, it is never the entire story. Presumably the chips handle more per cycle. So, before you jump to the extra cost of 64bit machines; you might want to wait for benchmarks.

    Dual-Core Chips - Now the appearance of dual-core chips is another matter altogether. These chips, when they become available, could very well significantly improve performance. But, obtaining this improvement will require substantial software changes. I am planning to make those changes to CVData/CVCX as this is a far more promising area. Actually, I've been planning these changes for years and the basic architecture of CV simulators was designed with this in mind.