Kevin,
Re: " I'd actually like to hear from some of the more technically minded
people if my working theory is correct--specifically, that one reason Intel can clock its
chips faster is that Slot 1 is a superior device for dissipating heat ..."
Slot 1 has very little to do with the fact that Intel can achieve higher
clock speeds than AMD. Please re-read my previous post to you and focus
on the performance part of the post. In summary, the reason that Intel
achieves higher clock speeds is due to Intel's FET/device design that
optimizes/maximizes the device drive current (Idsat) at a lower operating
supply voltage (1.8V @ .25um). Please note that for the same Idsat drive
current, a lower supply voltage process will always clock at higher speeds.
exchange2000.com
Re: "Idsat will not remain the same, it will go up with voltage."
You have asked a very good question ... let me explain. A process
generation is typically defined by the printed poly gate length. For
a fixed gate length, your are correct ... Idsat does go up with voltage.
Idsat also goes up as gate length gets smaller. The other constraint
is that as gate length gets smaller, the voltage that can be applied
across the device (and gate) also has to go down. The two equations
that we are trying to optimize are:
Power ~ CV^2f , C = Capacitance, V = Operating Voltage, f = Frequency
Performance ~ I/(CV) , I = Idsat, C = Capacitance, V = Operating Voltage
It has been interesting that from process generation to generation,
Idsat and capacitance have stayed relatively constant ... for example
.35 generation - Idsat = ~625ua/um @ 2.5V, Lgate = .28um
.25 generation - Idsat = ~600ua/um @ 1.8V, Lgate = .22um
So in developing a process for optimum performance, one needs to optimize
the device drive current at low operating voltages. The processes
to optimize are gate thickness, Source/Drain implants, channel implants,
gate length ... The company that achieves the highest drive currents
at the lowest operating voltages win in both performance AND power.
I believe that AMD's process probably gives the following:
.25 - Idsat = ~600ua/um @ 2.1V, Lgate = .25um (my estimate of gate length)
Therefore, their devices (CPU's) will dissipate more power and will have
lower performance. I think the data on AMD's power/performance prove
my statements.
Hopefully this helps."
Kevin, please spend some time "digesting" this post as this answers many
of your questions.
Make It So,
Yousef |
