These sites are looking only at the CPU itself — which, logically, should run hotter under many circumstances due to the fact that it integrates so many components which weren’t on the CPU chip (calling it an SoC – “System on a Chip” — would be much more accurate than calling it a regular processor) in previous generations e.g. Core 2 — not the entire chipset, which actually *reduces* the space, power and heat produced by the system.

We did hear that a lot of work has gone into the new cooling system, which takes back all of the space saved by the new chipset and other components which are also smaller than their predecessors….in fact, said cooling design is apparently more responsible for the “delays” in bringing this system to market than any other factor.

All that said; we can’t say with absolute certainty that the machines we get sneak peeks at in the prototype stage will be brought to market essentially unchanged. Small differences are almost a certainty — but something as big as rolling back to dual-core Nehalem only would be one heck of a big change.

Perhaps only the high end version will include quad cores — and perhaps it won’t be the top-end 2.93GHz chip, since only BTO versions of current iMacs run at above 2.8GHz anyway….but there’s very little chance that it will skip the Nehalem revolution entirely; Core i7 is just way too far ahead of other options in the Core 2 family, even in the dual-core versions of said chips, to miss out on.

That would put the iMac at a huge disadvantage against its competitors — granted, most “integrated desktop” PCs have the same basic requirements in terms of thermal envelope as the iMac, but many consumers evaluate a wide range of desktop options against the iMac and it needs to be able to keep up if not crush them outright.

We are more than willing to grant the possibility that the immediate-next generation of iMacs could be stuck with dual core for the time being, despite the strength of (and our confidence in!) our sources’ confirmation on the opposite…..but the possibility that they won’t be Nehalem at all is a lot more remote. Pretty close to zero, though we know better than to say anything with absolute certainty in the rumor-mongering game.

Otherwise it wouldn’t be a rumor, would it!

As for power concerns….yes, the high-end 2.93GHz quad-core Nehalem desktop chip draws more peak/avg power than all other versions — 130 watts versus 90. However, its temperature levels aren’t necessarily quite as high as people seem to think. Several new technologies introduced in Nehalem, from disabling individual cores entirely when not in use to dynamically scaling each core’s clock speeds independently, among *many* other things…..make it quite unlikely that the temperature of these new chips will remotely resemble older chips, even a single generation older, with similar power dissipation levels.

So, while we understand where these doubts come from….we’re not sold on their solidity just yet. However, we’re more than open to being provided technical details that back up such doubts! By all means — we’d rather be wrong once than wrong repeatedly! Confidence is the enemy of a rumor-monger, if you ask us. And we’ve had a decade and a half in the game (longer, before we were publishing it on the Web!)….so we know all too well the truth of that principle.

1333MHz DDR3 is only supported by the “Gainestown” Core i7 Xeon chipset — and only in the 2.8, 3.0, & 3.2GHz versions.

So, it’s not possible for the iMac, which will use the standard non-Xeon Nehalem chips, to use 1333MHz memory — but even so, the leap from two-channel DDR2-800 to triple-channel DDR3-1066 is quite simply huge! Offers just about double the raw memory bandwidth…and when you add in the new on-chip memory controller & low-latency on-chip “QuickPath” interconnects, the difference becomes truly huge.

In fact there is no reason why Apple *has* to use DDR3-1333 on the new Mac Pro; they could go with 1066 instead but that would leave it at a disadvantage against the competition. One possibility is the entry-level eight core model could have the slower 1066MHz RAM & the rest run at 1333. We hope to be able to clarify that well in advance of the new Mac Pros’ release near the end of March….be sure to keep an eye on this thread since there will be further discussion here in the comments!

Second only to a full blown Mac Pro, a new Nehalem iMac with quad cores and eight total threads (HyperThreading allows two threads per core) is going to be great for that. Particularly if they do in fact release a model with SLI (nVIDIA) or CrossFire (ATi) dual-GPU support.

As for when….the basic chipsets already exist, and have for many weeks now. The Mac Pro won’t go Nehalem until after Intel starts shipping Core i7 Xeons around the end of March; the closer we get to that time frame without an iMac update, the more ambitious that update will tend to be.

We truly don’t think that the iMac will be updated long after the Mac Pro, and quite possibly may precede it by a little bit….that could mean almost any time between now and the middle of April.

Hopefully, we’ll have more detailed and specific information on announcement/shipping dates in our next article on the subject which should be posted soon.