A Pentium M does not have HT. A Pentium 4 has HT. A processor that has an extremely long pipeline like the Pentium 4 is capable of using HT. A Pentium M with a small piepline cannot use HT because of lower clock speeds. However, a lower pipelined processor is much better. HT is not critical, but it improves performance on a processor like the Pentium 4 by 5-10% which is a large gain. It helps to execute two threads at once and this really helps.