I assume you mean either the PEP66 or the PAL6035 - and 54C is too high for both of those. It'll either be down to the contact between the hsf and the core (hsf not sitting level, or not enough/too much thermal paste) - or more likely, inadequate air flow in the case. With my 6035 on my tbird I switched off all my case fans and covered the holes, to simulate an ordinary case, and temps rose from 44C max to 59C - then the comp crashed! In that case I had a 120mm 105cfm fan sucking in at the bottom, and one exhausting at the top (though they were running at about 8V, so the air flow would be less). That just shows how much air flow matters - add a few more fans and watch those temps drop!