As long as the circuit is not changed that much(i. the die size), the cost of PII cpus
will be pretty much the same from lot to lot if the process is stable
, be it 133Mhz, 166Mhz, 200Mhz, 233 Mhz, 266Mhz,300Mhz,333Mhz, 400Mhz!!When I said you can sort different grades of CPU from the same
wafer, I just try to tell people that different grades of CPUs can be
manufactured from the same wfer. Yes, the real sort should be on the packaged units, the package will have an impact on the speed too due
to capacitance.
As you know there are many factors which will have an impact on the speed of circuits, but all in all to get the highest speed, you have to reduce the resistance and capacitance, and make the effective
channel length as shor as possible without lower the breakdown voltage too much. So the optimize the speed, you have first find out the critical path first, then you start to twist the process , you can
reduce the junction depth of drain and source to reduce the junction cap,or increase the intedielectric layer thickness to reduce the inter
dielectric cap, or increase tthe metal line thickness to reduce the
resistance, or push the lateral diffusion to push the effective
channel length(which may reduce the Vth to increase the switching speed of transistors), Or adjust the dose of channel implant to
optimize the Vth...... etc. For the higher speed, i.e greater than
300 Mhz, if the circuit is not redesigned, you may gain additional
speed by shrinking the transistor, example, shrink from 0.35um to 0.3um,you need just relayout the circuits and twist the process little bit. The yield may be changed, but the gross dies are also increased as a result og transistor shrinkage. So the cost of 133 Mhz PII will
be very close to that of 400 or 433... PII CPUS, as long as there
is major change of logics of circuit which will change the total die size!!!!!!!!!!!! Now, you will roughly know INTEL's margins !!!!!!! |
