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st: Stata for 64bit Mac


From   kturner@stata.com (Kevin Turner)
To   statalist@hsphsun2.harvard.edu
Subject   st: Stata for 64bit Mac
Date   Tue, 24 Jun 2003 14:16:35 -0500

Apple's release of the 64bit G5 processor yesterday has generated a lot of 
interest in Stata's future support for the new Macs and what the performance 
benefits might be. 

With regards to the most common questions we have recieved...

1. Timeline for 64bit Mac version of Stata

	Apple will not begin selling the G5 until August, so 
	Stata will not have a G5 for development purposes until 
	August (at the earliest). After that crucial step, it is 
	anyone's guess. Porting to 64bit isn't hard but the release 
	might be dependent upon a few other factors. We anticipate 
	that the 64bit version would be available as a free update 
	to current Stata8 users.

2. Will the current version of Stata for Macintosh run on a G5? 

	The G5 is capable of running 32bit and 64bit applications
	simultaneously. Of course, only the applications that are 
	designed for 64bit will be able to fully take advantage of the
	processor. 
	
	Existing versions of Stata will run on a G5 under the 32bit 
	mode.

3. Larger datasets 

	When a 64bit version of Stata is released for Mac, the primary 
	advantage will be the ability to work with very large datasets
	(datasets larger than the 32bit limit, or roughly 2 gigabytes).
	Stata would be able to access datasets that are theoretically
	as large as 4 terabyes (2^42) but performance will depend 
	largely on the amount of physical memory (RAM) installed. 

	See Apple's website (http://www.apple.com/g5/architecture.html)
	for more information on the amount of RAM you can install.

4. Will two double-precision FPUs increase precision of Stata variables?

	This will not increase the precision of Stata variables. 

	Why? 
	On previous 32bit processors, double-type floating point numbers
	were always 64bit (or 8 bytes). They were handled on a 32bit 
	processor by allowing the processor to work on the first 32bits
	(4 bytes) and then the second set of 32bits before combining
	the result. So, on older 32bit machines, it took 2 processor
	cycles for every 1 double-type. 

	With the new 64bit G5, 1 double-type can be handled in just
	1 processor cycle, and with 2 FPUs available this allows 
	for 2 double-types to be computed in the same cycle where an 
	older 32bit Mac would have taken a total 4 cycles. 
	
	The net result is a faster processor, not higher precision.

5. Velocity Engine

	The velocity engine is an independent issue with regards to 
	the 64bit G5, so a 64bit version of Stata on Macintosh will NOT 
	necessarily take advantage of the velocity engine. Support
	could be added for the velocity engine in the future but 
	Stata currently does not use it. 

	The velocity engine is a processor-specific set of routines
	that allow operations on 128bit 'chunks' of data.


Hope this clarifies some of issues concerning the new G5 and Stata.

--Kevin 
kturner@stata.com
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