I have not been able to blog here due to two reasons. One I got lazy, two is first as the same. Any way now i have woken up from my slumber. This neat article talks about a new 8 core chip ( for servers) from Intel. However, have you ever wondered why suddenly there was a paradigm shift from having faster chips (3GHz or more) to having more cores?
The main reason ( though there might be many others) is the problem of heat dissipiation. Just to give a little bit more information in this regard i will try to go a bit below the layer. The modern chips are all based on CMOS technology. Though most magazines call them as transistors they are really MOSFET's ( which means MOS Feild Effect Transistors). CMOS has this wonderful property that it consumes literally no power when it is holding a logic 'O' or logic '1'. So why the power loss? The power loss really occurs when there is a switching of the CMOS from the logic '0' to logic '1' or visa versa.
This means that more you switch the transistor the more heat you dissipiate. The more heat you dissipate the more cooling need for your chip. Now we are left with two options, either ensure that we cool the chip well or we reduce the heat generated. To a great extent we can cool the chip by adding bigger fans and heat sinks, however there is a limit to this ( because the heat generated takes a finite amount of time to get carried out and be dissipiated!!). If we concentrate on the second option we observe that if we do not switch the transistors so fast we can control the heating. This is what Intel has chosen to do by not trying to pump up the gigahertz. However, to boost performance now there are two cores ( which run at a slower rate!!) which can parallely execute instructions which are not directly dependent on each other . The story i am sure is more than this and i am not technically competant enough to put in that stuff here. However, someone i know does. I would be requesting him to add a few lines to this blog in a few days.
Please leave your comment if you have one. You can subscribe to this blog by using the links under "Subscribe" section.
The main reason ( though there might be many others) is the problem of heat dissipiation. Just to give a little bit more information in this regard i will try to go a bit below the layer. The modern chips are all based on CMOS technology. Though most magazines call them as transistors they are really MOSFET's ( which means MOS Feild Effect Transistors). CMOS has this wonderful property that it consumes literally no power when it is holding a logic 'O' or logic '1'. So why the power loss? The power loss really occurs when there is a switching of the CMOS from the logic '0' to logic '1' or visa versa.
This means that more you switch the transistor the more heat you dissipiate. The more heat you dissipate the more cooling need for your chip. Now we are left with two options, either ensure that we cool the chip well or we reduce the heat generated. To a great extent we can cool the chip by adding bigger fans and heat sinks, however there is a limit to this ( because the heat generated takes a finite amount of time to get carried out and be dissipiated!!). If we concentrate on the second option we observe that if we do not switch the transistors so fast we can control the heating. This is what Intel has chosen to do by not trying to pump up the gigahertz. However, to boost performance now there are two cores ( which run at a slower rate!!) which can parallely execute instructions which are not directly dependent on each other . The story i am sure is more than this and i am not technically competant enough to put in that stuff here. However, someone i know does. I would be requesting him to add a few lines to this blog in a few days.
Please leave your comment if you have one. You can subscribe to this blog by using the links under "Subscribe" section.
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I would want to write a few more things related to this article :)
ReplyDeleteI agree with Deepak that heat dissipation was one of the major concerns for the IC manufacturers to decelerate the growth of faster chips..
You rightly said that MOSFET consumes power during transition phase. This power consumption is called "dynamic" power consumption. However CMOS also suffers from "static" power consumption. By static power consumption, I mean the power dissipated by the device when it is in the OFF/ON state!! Ideally current flowing through the device should be zero in the OFF state. But in the real world, there is a small amount of current called "Sub - threshold" current flowing even though CMOS is OFF.
Sub threshold current was minimal and negligible when the chips were fairly big enough. Hence, it was not a major concern during those times!!
As we started approaching nano-technology, number of transistors/chip were increasing, power supply was reducing, size was shrinking. Static energy dissipation ended up being a bigger concern than power loss during switching!!!
Why static power consumption increases with reduction in size is a topic in itself and surely deserves a separate article:)
Interesting analysis were done and it was predicted that, if frequencies went on rising higher and higher, The cooling equipments required for them would end up in fans, coolers, bigger fans, water cooler A/C and what not!!!!
The coolers would turn out to be more dearer than the chips !!
Hence, it led to innovation of multi-core processors that rely heavily on parallel processing and pipe-lining techniques.