The 533 is designed for entirely different memory than the 533-C. The 533 uses the new 32-bit modules which can be mounted singly, but are very hard to find. The 533-C uses the normal 16-bit type that are easy to find and must be installed in pairs. That's why one board has two slots and the other has four, by the way.
<font color=blue>By now you're probably wishing you had asked more questions first!</font color=blue>