[rescue] Difference between U5/10?

[James Hartley]

I was under the impression that the motherboards between the Ultra 5 and
Ultra 10 were the same.  From what I have seen on this list, the fastest
CPU marketed for the U10 was 440MHz.  If this is all true, is there
anything preventing moving U10 mobo's back to a U5?
 
>From what I can see, besides more plastic, the U10 offered four PCI
slots as opposed to three in the U5.
 
Thanks.
 
j