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Re: JVM on G5

On Mar 31, 2004, at 5:33 AM, Carron, Kris wrote:

I was wondering if the JVM on Mac OS X 'adjusts' itself to make use of
specific processor capabilities, for instance the processing power of the
64-bit PowerPC G5. More specifically, does the JVM 'behave' differently on
such a processor with respect to floating point calculations, use of the
Java long (64-bit) datatype, dual processor, etc. Or is it the exact same
JVM as on a 32-bit architecture?

Apple's JVM will use different code and optimizations when running on different processors (I would imagine the JIT compiler will get better at utilizing the G5 as Apple refines it). The JVM does use the 64 bit integer abilities of the G5 and for long integer types (floating point support 64 bit math already existed). IIRC Apple's JVM supports multiprocessors at the Java thread level, it does not require a G5 for that just multiple processors.

If so, are there any JVM startup options or other steps one can take to
improve the speed of floating-point operations on such hardware?

Don't know of any... but IIRC floating point on G3/G4/G5 are generally the same in capabilities (bit width) but obviously not performance (the G5 does rather well). You may want to consider touching AltiVec if you need the best performance (depending on what operations and widths you are working on).

-Shawn
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References: 
 >JVM on G5 (From: "Carron, Kris" <email@hidden>)



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