Have finally got round to investigating the problem. Repalced ram with Crucial DDR2 667. It will now POST to 256 MHz with PCIE Aysnc at 114MHz. NB There is a PCI bus lock so that keeps it at 33.3MHz anyway. DRAM timings are from SPD (makes no diff if not). These are at 255.8 MHz and a 1:1 ratio: 3,3,3,9,12 What I think is killing the overclock potential is the Vcore - I can only use Auto or High usefully (haven't tried Low). Thishas resulted in a Vcore pretty much the same as stock at 200MHz; 1.2v Any suggestions to unlock the potental of the E4400?