Speed in IC’s : A major concern

Firstly let me ask what strikes your mind first when I say performance?
Intel started designing processors with MHz to GHz frequencies (Improving the performance of course, but if we see the advantage there might be some flaws too). Yes serially it was possible to send and receive the data fast, but consequently faster was the rate of power consumption. Then came the low power techniques like clock gating and power gating into limelight. Clock gating as the word says it simply means gating the clock.

Why to waste the clock every time, if data is controlled by another signal? But bringing a gate into the clock path is something playing with the highest priority signal & something similar was with power gating where few sections of the circuit when not in use were shutted off.

While many companies like Intel, Soctronics etc are already busy working on 14nm technology as area is what market always demanded throughout the years for small size and light weight products, the catch is less the area a system takes, more the devices an IC eat and more the devices an IC have more is the logic so is the functionality. This reminds me of how Jack S kilby have thought of bringing “Integration of circuits” where devices started shrinking as width kept on decreasing with what the wire resistance and its internal capacitance decreased as well.

Now as delay decreases the time it takes for the electron to travel from one point to another, the frequency of operation increases.  This is what we have seen and should continue right? It is like Few years back SONY laptops faced some complaints from the users that the system after a year or so started producing humming sound in some of its products running at 3 GHz clock. This noise was even louder then desktop systems, its like a bowing plane, I don’t want to detail it but yeah you must have heard that. The system would even go so hot, you just can’t afford allowing it to rest on your lap. Yes, the frustrating sound invoked within was from the fans used required to compensate the heat produced due to continues switching of signals.
Experiencing the same some smart one’s will definitely try for re installations but  that really is not a reliable solution. Picking any another, fan noise should only come into picture if you are using lots of tabs at a time but here the sounds momentarily continues even when it is in a complete “shut down condition” or when it shows (0 % CPU usage and 25% memory usage) still it continues to do its job.

Anyways, what made this happen…? and what made the speed a limitations now instead with the device shrinking the speed should actually keep on increasing.

To answer this question it is important to know:

• What exactly the size of Silicon Dioxide molecule is ?
• Should we ignore the wire delays which connects the macros (i.e transistors) at this level.

Switching speed is decided by how strong the electric field is. If the device shrinks the area should reduce and this reduces the distance between the two plates (Gate and Channel) which eventually results into stronger and stronger field. But the molecular size of silicon dioxide is approx. 0.09nm (for 45nm technology) which indeed shows a limitation you just can’t reduce further. Hence more reduction in area after 45nm results in more power consumption but no subsequent increase in speed (frequency of operation). Moreover with channel length going beyond quite a few nano-meter, the wire capacitance and resistance will play an important role deciding the delays hence, cannot be ignored. So frequency of operation is an important issue now.

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This is a guest post by Shiven Pandya