A bit of defense for SOI

I have received intelligent criticism about my enthusiasm for AMD doing the extra expenses it takes to include SOI in their silicon manufacturing, to which I gave a reply, but a new article allowed me to go deeper into the subject:

In an interview, "Turn Down the Heat ... Please" which I obtained thanks to an article in "The Register", "IBM: Cell-like CPU yields 10-20 per cent", Ed Sperling asked Tom Reeves, VP of semiconductor and technology services at IBM, what would be the next big thing in chip technology, and Mr. Reeves answered:

Through the ’70s and early ’80s, bipolars went up to 100 watts. We had water-cooling systems, but you needed something new. Then we started with CMOS, [...] Now, 20 years later, we’ve got 100 to 120 watt chips again. Power is everything. The efforts we’re taking to get leakage power down for cell phones or a base station or a Cisco switch are enormous. If you look at a chip in a base station or a switch, they’re 40 watts, and there are a lot of them. The total wattage gets up to 5,000 or 10,000 [!!]. So the major focus now is not on Moore’s Law [!!] and how you get the next density step. We’ll get that. How you get the next performance step is harder work than it’s been, too. But the most important issue is how you manage power. Leakage power at the most advanced lithography is very challenging. And with active power, can you cool the gain? College kids were hanging some gaming systems out their dorm windows to cool them down.

Silicon on Insulator may not help at all to overclock a µ-processor, which is a nice feature that the gaming market appreciates (the materials used for SOI are good heat insulators as well, thus they obstruct the efforts to extract the extra heat that the overclocker forces the processor to generate over volting and over clocking it), but still, it helps with the very important leakage.

The simplistic explanation is this: The transistor behaves a bit as a capacitor, to switch, it needs to get rid of the charge it accumulated. The lower the charge, the lower the energy leakage associated with switching, and the lower the capacitance the lower the charge. SOI helps precisely about lowering the capacitance. According to the wikipedia, SOI helps 30% with the transistor leakage, and 15% with switching speed (of course, it takes less time to get rid of a lower charge at the same current level (because the voltage is the same and the resistance too)).

We shouldn't take Mr. Reeves opinion as that of an interested party, what he points out is perfectly clear and true. Power, it is Power the issue of these times. The usage of the more expensive SOI technology, and harder to market slow clock speeds, is a sign of a pervasive attitude at AMD: They focus on solving the real technology issues. Just like I said in "65nm Is Just Intel Marketing", Intel doesn't bother, at Intel, the basic question is this: "Can we market technology defficient products?", if the answer is positive, Intel won't do power efficient processors, nor good architectural features. Rather, what Intel attempts is to sell products with marketing-amiable catchphrases such as "Gigahertz" (remember that Pentium 4s only cared about the clock speed, although they couldn't do as much real processing as an Athlon at half the speed, while consuming a lot of power!), "Hyperthreading", which was so poorly implemented that rather than providing a huge speed boost, as it should, provides a decline. 65nm products that so far are not even at par with current AMD products. "Dual Cores" that are really multi chip packages, and it now spins the weaknesses of not having neither the integrated memory controller nor a processor interconnect as a great advantage that "allows" to put gigantic caches and a stupid memory architecture flexibility, because it's something you can't do much with.

It is the same approach everywhere. For server processors: "Can we market processors for servers although they can't scale past the four cores because they don't have any processor interconnect?", "Can we fool our customers with Netbursts while they want to buy Woodcrests?", yeah, let's name the Dempseys Xeon 5000 series and the Woodcrests Xeon 5100. A great question is how long can Intel succeed with lies. It has taken decades to merely crack Intel's monopoly, which was constructed with lies and deception. How long would the monopoly remain given that Intel insists in blatant lies?

There is no wonder that at Intel they don't expend the extra doing SOI, they prefer to expend expend extra in marketing to convince people that SOI is an unnecessary expense.