Programming with FASM – test 64 bit CPU compatibility.

By | 28/08/2018

The easy way is to check the incrementing the eax register:
The problem is much more complex if we are to discuss the subject.
Let’s see the source code:

The x64 and x86 are symbols.
The source code shows us the algorithm:

  • recall correctly the EAX with  xor ;
  • try to  incrementing the EAX with inc and nop ( the nop –  command that does nothing , in this case will use the addressing mode to test with jz and jnz ) ;
  • if not then EAX cannot be increment ( the inc instruction increments the contents of its operand by one the result will jump at x86 source code area, ZF =0 ) ;

NOTE: If you tell me this solution is full of problems then I agree with you (see: inc sets ZF if the value of cl after the increment is zero). There is also the possibility to test the processor directly. This source code just shows a simple model of CPU capability testing.

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