One (delayed) follow-up question on this: We are buying Dell workstations with 64-bit single-core Xeon processors, and we could add a second processor for not much more. Is it possible to make a generalized statement as to what kind of performance improvement we would see with a single vs. dual processors when running R on these systems? Thanks again. M. -----Original Message----- From: Thomas Lumley [mailto:tlumley at u.washington.edu] Sent: Friday, September 02, 2005 1:29 PM To: Martin Maechler Cc: R-devel at r-project.org; Milton Lopez Subject: Re: [Rd] 64 bit R for Windows On *Windows* there is an address space limit of about 3Gb (and on other 32bit systems) On a 64bit system the limit is that a vector can't have length greater than 2^31, but this would be 8Gb for integers or 16Gb for doubles and so represents larger objects than you would want to handle on most current 64-bit systems. -thomas