The Economics of Chips With Many Cores

meanonymous writes "HPCWire reports that a unique marketing model for 'manycore' processors is being proposed by University of Illinois at Urbana-Champaign researchers. The current economic model has customers purchasing systems containing processors that meet the average or worst-case computation needs of their applications. The researchers contend that the increasing number of cores complicates the matching of performance needs and applications and makes the cost of buying idle computing power increasingly prohibitive. They speculate that the customer will typically require fewer cores than are physically on the chip, but may want to use more of them in certain instances. They suggest that chips be developed in a manner that allows users to pay only for the computing power they need rather than the peak computing power that is physically present. By incorporating small pieces of logic into the processor, the vendor can enable and disable individual cores, and they offer five models that allow dynamic adjustment of the chip's available processing power."

Comments

You know what I don't get?

[Moraelin]

You know what I still don't get? Why's everyone acting like dividing a CPU into several separate cores is a good thing?

Let me compare it to, say, a construction company having a number of teams and a number of resources, e.g., vehicles:

1. One team, 4 vehicles. That's classic single core. Downside, at a given moment it might only need 2 or 3 of those vehicles. (E.g., once you're done digging the foundation, you have a lot less need of the bulldozer.)

2. Two teams, can pick what they need from a common pool of 4 vehicles. That's classic "hyperthreading". Downside, you're not getting twice the work done. Upside, you still paid only for 4 vehicles, and you're likely to get more out of them.

3. Two teams, each with 4 vehicles of its own. They can't borrow one from each other. This is "dual core." Downside, now any waste from point 1 is doubled.

But the one I don't see is, say,

4. Two teams with a common pool of 8 vehicles. It's got to be more efficient than number 3.

Basically #4 is the logical extension of hyperthreading, and it seems to me more efficient any way you want to slice it. Even if you add HT to dual-core design, you end up with twice #2 instead of #4 with 4 teams and a common pool. There is no reason why splitting the pool of resources (be it construction vehicles or execution pipelines) should be more efficient than having them all in a larger dynamically-allocated pool.

So why _are_ we doing that stupidity? Just because AMD at one point couldn't get hyperthreading right and had its marketers convince everyone that worse is better, and up is down?

Calculators

[Detritus]

Someone already mentioned mainframes. Something similar is often done with calculators. Rather than design a new chip for each model, they design a single chip with all of the features. In mid-range and low-end models, it is crippled by the design of the keyboard and/or jumpers. It is often cheaper to dumb down a single hardware design than to produce unique designs for each segment of the market.