Question

to improve the data transfer performance, which choice is better: (1) to widen the data bus from 16-bit to 32-bit; or (2) to double the external clock frequency of the bus clock from 8-mhz to 16-mhz?

Answer 1

It's better to double the external clock frequency of the bus clock from 8 MHz to 16 MHz.

Widening the data bus lets us send more data in a cycle. This is useful in some situations but it can come with a series of challenges:

• The whole system must be adapted for a widening of the data bus. This is a hard and expensive process.
• There are situations where we only need a word or we can't decide what memory address we need to get next from memory, but only after the current word is processed. This makes the widening useless.

On the other hand, doubling the frequency is always useful. This makes the cycles shorter and getting the data from memory much faster. This is usually the bottleneck so the computer will surely benefit from this change. This is what has been happening in the last "computer era" with new DDR standards.