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Old 11-29-2005, 02:21 PM   #1
schneidz
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jpm: java physical machine


i dont know if this belongs in programming or hardware.

i always hear complaints that java programs are trés slow. this is most likely because java isn't necessarily cross-platform. it only runs on 1 platform (jvm) and no matter what the implimentation, there is always a level of emulation to convert java byte code to the native processor's machine language.

I would like opinions on why a processor hasnt been built that can inately read the byte code in a java class file and interpret each instruction as its native machine language.

thanks,
any opinion is welcome.
 
Old 11-29-2005, 02:38 PM   #2
jlliagre
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The complaints about java being slow are essentially no more true.
Some java applications may still be slow these days, but the reason is usually they are poorly written.

Several processors were built to natively accept bytecode (ultrajava, picojava), I doubt they ever left Sun laboratories.
 
Old 12-01-2005, 01:25 PM   #3
schneidz
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thanks jlliagre for posting about pico/ micro/ ultra-java, that answers my question (so something does exist...).

i couldnt find mention of mention any respective assembly language (java cannot be an assembly language).

I am a hardware engineer and i am curious to find a table of supported machine language opcodes and their function (such as in 65c02, loading the accumulator with the number 3 yeilds the hexcode instruction '05 03' or in x86 to add the immediate value 3 to the 'eax' register it would be '04 03').

does anyone have any idea of getting this info short of being a sun systems programmer.

thansk,

Last edited by schneidz; 12-01-2005 at 03:17 PM.
 
Old 12-01-2005, 04:26 PM   #4
vladmihaisima
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Java translates into Java bytecode. You could read this for info java vm .

About hardware running java, ARM also implemented more instructions into its processor to make Java faster (search google for Jazelle).

Hope this helps
 
Old 12-01-2005, 08:47 PM   #5
schneidz
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this page also helps: http://java.sun.com/docs/books/vmspe...onics.doc.html

i didnt know java had an assembly language. now to figure out what each opcode + parameters means.

any pico/ micro/ ultra-java programmers out there?
 
Old 12-02-2005, 01:26 AM   #6
jlliagre
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Opcode and parameters meaning is described in the vladmihaisima's link: 3.11 Instruction Set Summary.

You may want to know that there are also quite a large number of interpreted and compiled non-java languages implementations that exist on top of the JVM:
http://www.robert-tolksdorf.de/vmlanguages.html
 
Old 12-04-2005, 12:04 PM   #7
schneidz
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thx again jlliagre, this is quite much info
 
  


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