Backward compatibility between SATA150 and SATA300 devices was intended, therefore SATA300 controllers were designed to fall back to SATA150 speed when connected to such drives. However, in practice some older SATA controllers do not implement SATA speed negotiation properly, and you can not be a 100% sure that a SATA300 hard drive will fit your sata150-vs-sata300/" class="more-link">More >