Question

4. The heart of the original Apple iPad is the Apple A4 chip which operates at 1.0 GHz and is believed to utilize ARM Cortex-A8 CPUs built with Samsung 45nm technology. Assume it dissipates 5 watts using a 1.1 V power supply.

a) If a prototype made in 65 nm is available, what speed and power consumption will the chip likely have assuming constant-field scaling?

b) If the supply voltage on the 65 nm part were scaled to 0.7 V, what will the power consumption and speed be then?

c) i) What supply voltage should be used by the 45 nm part to set the power consumption of 2.5 Watts?

ii) At what speed would the processor then operate?

Answer 1

(1) If technology scales by 1/S, then for constant field scaling

                                                            

                                                              

                                                               

So power is

                                                        

Here

                                                                          

So

                                                              

So

                                                          

Speed is given by

                                                                   

Or

                                                                 

(b) In this case

                                                        

Also

                                                        

So

                                                      

Or,

                                                             

Also

                                                          

So

                                                                              

Or,

                                                                            

(c) Now

                                                                  

but

                                                                     

                                                               

So

                                                            

So

                                                                      

Or

                                                                        

Now

                                                                       

So

                                                                   

Or