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st: Stata for 64bit Mac
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
Existing versions of Stata will run on a G5 under the 32bit
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.
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.
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