Thursday, February 16, 2006

65nm is just Intel Marketing

There has been a lot of nonsense talk about the supposed advantages of intel processors at 65nm. I am fed up of watching my friends at AMD repeat the mistake. Read if you want to get out of the darkness, bear with me about the technicalities:

First fallacy: It is cheaper to manufacture the same number of transistors at 65nm than 90nm:

It is clear that a wafer of 65nm has the potential to have 92% more transistors than a wafer of the same size with 90nm features. But wafers at 65nm are much-much-much harder to do. In particular, to obtain the same yields (percentage of perfect circuits), you have to expend much more. A quick an easy way to do 65nm, or 45, or whatever, is just do them, and allow the yields to crash through the floor. If AMD wants to rush to 65nm, it can do so sacrificing the yields. Therefore, I am not impressed by Intel's 65nm tech. before knowing about the corresponding yields. I see something very interesting: Intel's dual cores have been dual dies before Yonah/Sossaman, that is, two different circuits glued toghether. That tells me that Intel's yields should be significantly worse than AMD's 90nm 95%. A bit of technicallity: The larger a circuit is, the greater the probability of having a defect in manufacturing. Specifically, for a single die dual core to be perfect, both cores should be perfect too, therefore, the probability of defects is squared. I don't know the exact numbers, but Intel's yields at 65nm shouldn't be more than 60%. That means that single die dual cores would have about 36% yield, roughly half of single dies. There it goes the 65nm size advantage. But the process is still much more expensive. And because Intel has this huge architectural deficiencies, such as the Front Side Bus, it has to abhor to use memory and is forced to compensate with large caches, that once again have the yields decreasing at its square.

[Full analysis: Let's say one cache has a yield of 3/4, and unitary cost. A cache double the size, costs twice at the same yield level, but since the yields becomes (3/4)^2 = 9/16 ~= 1/2, or a cost increase of (3/4)/(9/16) = 4/3 due to yields; then the total cost of a cache twice the size is 2.66. With 50% cache yields, (1/2)^2 = 1/4; (1/2)/(1/4) = 2; a total cost of 4, four times an unitary sized cache].

Things get really interesting when you consider QUAD cores: In the case of AMD, a 95% yield becomes a bearable 81%. Intel's... a 13%. The fact that Intel demonstrated a quad core which was in reality a double die of single die dual cores what proves is a) Intel wants to fool the industry with Public Relationships marketing shows, and b) very probably they don't have the capacity to do quad cores, therefore, the yields should be very small, and c) commercial products should be very far. Really, what did Intel do? they admitted defeat!

Thermal dissipation: It used to be that smaller transistors consumed less power. But not anymore. Before, the supporting infrastructure for integrated circuits consumed negligible power compared to what the transistors themselves consumed. But nowadays, because there are so many millions of gates in a microproc., and the internal buses are 64 bits wide at least, the consumption of the tiny wires has become significant. There is no way out of this: The wires are thinner, the resistance is higher, the lost power greater. Thus, the brute force approach, miniaturization, is becoming less and less attractive, because it has less to be gained. Comparatively speaking, and most importantly, Intel does Strained Silicon while AMD does Silicon on Insulator. SOI gives additional protection against another plague of the sub 100nm world: migrating currents. The gate, collector, and drain of transistors are so close that the transistor has trouble to really cut currents. This is an exponential problem, because the only way to compensate for the background electrical noise is to raise the voltage, raising migrating currents, a vicious cycle.

Switching speed: Oh!, yes, at 65nm is much faster. But the additional speed has a price. That's why all other processor manufacturers chose to improve the architecture rather than insist in the miniaturization, but Intel did kind of the opposite: Simplified the architecture to streamline it and make it more suitable for high speeds. The result? Eunuchs such as the Pentium4 that can't even do multiplication with a barrel shifter. Or the super deep pipelines that are just inefficient. For Intel, this was all a marketing game: To have the greater speed, the smaller feature size, because to evaluate performance is difficult, while the megahertz/nanometer number is catchy.

Intel has a manufacturing tech. of cloning factories to the cafeteria that simply is primitive, such as Sharikou detailed himself in one of his posts. AMD has APM, a robotic tech. for chips production, leaps and bounds ahead of Intel's. That's why when I hear Hector Ruiz saying that basically they will do 65nm as soon as AMD feels like it, I believe that it will be a success.

The bottom line is: Why would AMD want to disrrupt sold-out production of 90nm products to fiddle with inmature yields at 65nm? Let us the competition to rush and crash


Anonymous said...

Insightful post. Your argumentation is clear and the evidence obvious. I've bookmarked this blog and will check it daily. - Firefox opens all my bookmarks at once, then through the day I read and close them!

Eddie said...

Thank you. You should have left a name to address you properly.

I will try to write more to deserve being checked daily!

Anonymous said...

Interesting summary.

Anonymous said...

Good analysis

Eddie said...

This article has been partially updated here:

Anonymous said...

So this is just an AMD fanboy site then right? 65nm is cheaper to produce than 90nm after the initial captical expenditure. Your yield numbers are completely made up and therefore none of your arguments hold any merit. The fact that you even mention shakiruo as a valid source pigeonholes you as untrustworthy at best.

Eddie said...

Anonymous, you should leave a name to address you.

I am an AMD fan, also an investor, and so far I have lost some money too. I want to help my credibility by being open.

My numbers are educated guesses. No pretenses of being authoritative.

Mentioning Sharikou doesn't degrade the argument: Follow the logic.

As a matter of fact, this is an issue of logic, it doesn't matter who's words are these.

If you don't like the logic, why won't you point out the mistake? if my educated guesses about the yield numbers don't satisfy you, why won't you illustrate me which numbers may be correct?