On Moore’s Law
Moore’s law, attributed to one Gordon Moore, founder of Intel states that the number of transistors on an integrated circuit doubles every 18 months. Note, this has nothing to do with speed or power consumption, just the number.
Anyhow, a friend and I were discussing this last night. Intel’s problems with 90 nm lithography. TSMC’s difficulties even getting to 130 nm (0.13 micron). The reason this matters is simple - if you want to pack more transistors onto a device, you have to do something about the twin evils of power consumption and heat generation. Sure, you could (theoretically) make a Pentium4 with 55 million transistors on the same 1 micron technology that was used in the original Pentium. But it wouldn’t run at even 60 MHz without severe problems in power consumption, heat generation, etc.
So, the answers have traditionally been to shrink the “feature size” of devices on the chip. However, there are limitations that we run into very quickly. The primary on is not, as one might expect, physical. It is economical. We didn’t come up with a definitive answer, but we concluded that at some point it is going to cost too much to build a fab to make a chip to run that fast. Intel spent BILLIONS to make a 90nm process fab that runs on 300mm wafers. How many Prescotts do they need to make to break even?
Most chips are printed with a photolithograpy method, using ultraviolet light at 193 nm. Note, this is larger than the features being created by the mask on even 180 nm chips. There has been much talk of other lithographic methods, such as Extreme UV, and X-ray - both of which have not only technological but economic hurdles to clear. And as of 2004, Intel has not yet produced one chip on an EUV process.
And then we have the twin bogeymen of heat and power consumption. A Pentium 4 Prescott at 3.4 GHz is rated for a “thermal design power” (maximum thermal output) of 103W. This translates to CPU temperatures of 130-160 degrees (Thanks, [H]ard|OCP). By comparison, the 2 GHz Athlon XP sitting in my computer is idling at 109 degrees, and gets up to about 130 under load.
And if you’d like to add to the power consumption problems, put in one of nVidia or ATi’s next generation cards (6800U or x800) and you need a 420-500 watt power supply to start your computer!
I quickly becomes obvious that one of two things has to happen - either big changes are gonna come in the way chips are conceptualized and designed (multi-core low density chips perhaps) or better cooling solutions (liquid cooling that doesn’t leak?).