Inline ASM return QUAD

[mark smit]

Hello Everyone,

I need some pointers on how to get an inline asm function to return a quad. I'm playing around with making "unique" numbers so I though i would investigate the TimeStampCounter(RDTSC). This instruction returns it's result in EAX and EDX.

function GetTimeStamp() as quad
    asm dw &H0310F ;opcode for RDTSC
    asm mov function[0],eax
    asm mov function[4],edx
end function

This just doesn't do the job. I also want to know why the instruction RDTSC gives me a syntax error when used inline.

asm RDTSC **NO GO**

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Cheers!

[This message has been edited by mark smit (edited April 22, 2001).]

[Semen Matusovski]

RDTSC is Pentium specific instruction. Somehow I made some experiments and found this command unuseful under Windows.
A reason is simple - to have correct timing it's necessary to disabke interrupts (CLI/STI), but Windows (at least, Win2000) doesn't allow to do this.
As result - I ran a program several time and had different timing.

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E-MAIL: [email protected]

[mark smit]

Hello Semen,

For my purposes the counter accuracy is not important. I just need to know how an inline assembly function can return a quad type. But thanks for the information



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Cheers!

[Semen Matusovski]

Mark --
all works as expected and similar your function.

   #Compile Exe
   #Dim All
   #Register None
   
   %Lo = 123456
   %Hi = 7890   
   
   Function GetTimeStamp() As Quad
      ! MOV EAX, %Lo
      ! MOV Function, EAX
      ! MOV EAX, %Hi
      ! MOV Function[4], EAX
   End Function

   Function PbMain
      Dim x As Quad
      x = GetTimeStamp
      If Str$(x, 18) = Str$(%Lo + %Hi * &H100000000&&, 18) Then MsgBox "Ok"
   End Function

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E-MAIL: [email protected]

[Steve Hutchesson]

Mark,

This will do the job OK but be warned that as a timer, it suffers
interference from the operating system that makes its accuracy of
limited use.

In practical terms, GetTickCount() has the same effective resolution
once you calculate the average interference fromthe operating system.

  FUNCTION Get_RDTSC() as QUAD
  
      LOCAL BigVar as QUAD
  
      ! db &H0F, &HA2 ; CPUID < clear pipeline
      ! db &H0F, &H31 ; RDTSC < get timer
  
      ! mov BigVar[0], eax
      ! mov BigVar[4], edx
  
      FUNCTION = BigVar
  
  END FUNCTION

Regards,

[email protected]


[This message has been edited by Steve Hutchesson (edited April 22, 2001).]