I did the swap in a Performa 631 and it worked fine. Just be sure the 040 is rated at the same speed or higher than the LC you are replacing otherwise you will be overclocking the 040 and it may not stand up to it for long considering the age of any remaining 040 chips. The pathways inside the chips still deteriorate over time even when they are not in use, so overclocking is more likely to create short circuits in older chips.