Prime still varying in speed (last firmware)

[Oulan]

With the last firmware (and a factory reset) with the following prog

Code:

#pragma mode( separator(.,;) integer(h32) )
EXPORT Fourmi()
 BEGIN
 LOCAL DX:=[0,1,0,−1];
 LOCAL DY:=[1,0,−1,0];
 LOCAL ST:=TICKS;
 RECT();  // Clear screen
 160▶X;120▶Y;1▶D;0▶N;
 REPEAT
  IF GETPIX_P(X,Y) THEN
   (D MOD 4)+1▶D;
   PIXON_P(X,Y,#000000);
  ELSE
   ((D+2) MOD 4)+1▶D;
   PIXON_P(X,Y,#FFFFFF);
  END;
  (X+DX(D)) MOD 320▶X;
  (Y+DY(D)) MOD 240▶Y;
  N+1▶N;
 UNTIL GETKEY=41;  // shift key
 //FREEZE;
 RETURN 1000*N/(TICKS-ST);
END;

The speed still can be as slow as 293 it/sec and faster up to 11297 it/sec
This is quite strange ...