ssd, im using an old one and its 7.4, i dont trust wei but it is a good rough estimate, relatively speaking
Hitting 7.7 on a 120gb Sandisk Extreme SSD. was 5.9 previously on a 74gb Raptor. Change to a SSD if you want higer than 6.0 but honestly it wont affect your machine except in some loading times. Score is only a rough guide.