The Python mandelbrot program uses 4 cores the PHP mandelbrot program uses 1 - that's why Python seems so much faster on mandelbrot.<p>The Python spectral-norm program uses 4 cores the PHP spectral-norm program uses 1 - that's why Python seems so much faster on spectral-norm.<p>The Python binary-trees program uses 4 cores the PHP binary-trees program uses 1 - that's why Python seems so much faster on binary-trees.