Fibonacci..so slow by Recursion

$start = ""
MsgBox(0, "",_fibo(40) &@CRLF &"Spend: " &TimerDiff($start) &" Sec")

Func _fibo($f)
$start = TimerInit()
If $f <= 1 Then
Return 1
Else
Return _fibo($f - 1) + _fibo($f - 2)
EndIf
EndFunc

$start = ""
MsgBox(0, "", _fibloop(40) &@CRLF &"Spend: " &TimerDiff($start) &" Sec")
Func _fibloop($s)
$start = TimerInit()
$a = 1
$b = 1
For $i = 2 To $s
$temp = $a
$a = $a + $b
$b = $temp
Next
Return $a
EndFunc