32 bit softwares on 64 bit machine?

PC manufacturer will always ensure, at least at a reasonable extent, that popular software will run with them or else no one will buy them. The reason for the term backward compatibility. Almost all(if not all) 32 bit program will run on a 64bit platform. 32 bit programs could not just take advantage of the new features of 64 bit process simply because they are not aware of it when they are created. The question is, Will there be any performance boost? Assuming that the program take advantage of PC resources, like RAM and processor cache. The answer is YES. 64bit processor generally has bigger cache than 32 bit processors. But then again not as fast as programs build with 64bit encoding in mind.