Speed now & then
Jecel Assumpcao Jr.
jecel at merlintec.com
Wed Apr 11 13:31:47 CDT 2018
Chuck Guzis wrote on Wed, 11 Apr 2018 11:09:23 -0700
> I thought that Moore's "law" dealt only with the number of transistors
> on a die. Did Gordon also say something about performance?
That is correct. The observation that transistors would be faster and
use less power as they became smaller is called "Dennard scaling" from
This led to the MHz wars of the 1990s. Sadly, as the isolation barriers
(the "O" in "MOS") became thinner and thinner we could no longer ignore
leakage currents. In addition, going with lower voltages no longer was
possible as we got closer and closer to the transistor threashold
voltages. So we got stuck at 3 GHz or less.
Besides getting more performance with smaller transistors, we have also
been increasing performance by taking advantage of more transistors by
doing more stuff in parallel. So we went from up to dozens of clock
cycles per instructions to three or four instructions per clock cycle.
Quite a few of the additional transistors have been use for more and
more layers of caches.
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