Q$5.$

$//10$ points $(4+3+3)$

a$.$ In the IBM $360$ Models $65$ and $75,$ addresses are staggered in two separate main memory

units $($e$.$g$.,$ all even$-$numbered words in one unit and all odd$-$numbered words in

another$).$ What might be the purpose of this technique?

b$.$ While browsing at Billy Bob$$s computer store, you overhear a customer asking Billy

Bob what is the fastest computer in the store that he can buy. Billy Bob replies, $$You$$re

looking at our Macintoshes. The fastest Mac we have runs at a clock speed of $1\mathrm{.}2$ GHz$.$

If you really want the fastest machine, you should buy our $2\mathrm{.}4-$GHz Intel Pentium IV

instead.$$ Is Billy Bob correct? What would you say to help this customer?

c$.$ The ENIAC, a precursor to the ISA machine, was a decimal machine, in which each

register was represented by a ring of $10$ vacuum tubes. At any time, only one vacuum

tube was in the ON state, representing one of the $10$ decimal digits. Assuming that

ENIAC had the capability to have multiple vacuum tubes in the ON and OFF state

simultaneously, why is this representation $$wasteful$$ and what range of integer values

could we represent using the $10$ vacuum tubes?