Charles said:
Hi,
Sorry if this is a bit of a basic question but my understanding is that the
smaller you can make the devices the faster potentially they can perform.
However there is a limit. Considering the speed of processors in PC's has
increased from 100MHz or so to 3GHz, what is the fastest speed that will be
attainable?
There are many limiters for a chips speed, from raw transistor size up
to macro-scopic packaging.
At a packaging and manufacturer level, the CPU is spec'd to dissapate a
given themal power. It is easy to get faster speed by simply running
smaller transistor dimensions, but the off-state leakage exponentially
increases for only a linear increase in speed.
There are certainly others here who can comment more knowledgeably on
the design issues, but there are significant timing corrections to sync
signals that were more even more troublesome on Prescott than
Northwood.
At a transistor level, there are several technical challenges to
overcome. Typically, the gate oxide and transistor dimensions are
scaled with each technology generation to improve short-channel effects
and increase drive current. However, the SiON gate oxide is near its
limit and can't be scaled further without degrading oxide reliability.
The transistor dimension can be scaled down further (90nm -> 65nm
technology) which will decrease the parasitic gate-source/drain
capacitance and reduce transit time of carriers across the channel.
However, without gate oxide scaling these devices will suffer from
degraded short-channel effects.
-Greg