Nehalem Micro Architecture: Intel Embraces the IMC and IGP

Surprisingly, Intel gave away quite a few details about Nehalem. Although Nehalem is still based on the 4-issue Core architecture, it takes "multithreading" to a whole new level. First of all, Nehalem can contain up to eight cores per die. Combined with 2-way Simultaneous Multi-Threading (SMT or Hyper-Threading), you'll have the ability to execute up to 16 threads on one chip!

Nehalem will also use multi-level shared cache. Pat Gelsinger indicated that only the highest level of cache would be shared, meaning that Nehalem could very well have a similar cache hierarchy to AMD's Barcelona (independent L1/L2 caches per core, but a shared L3 cache). The power of each core is "dynamically managed" which might indicate that Nehalem goes one step further than AMD's Barcelona core: it could have independent power planes.

Nehalem will no longer use a FSB but a serial point to point interconnect. Even more revolutionary is the fact that Nehalem will have an integrated memory controller (IMC) and that the number of serial interconnects is variable (Intel's version of "HyperTransport"). Another potentially groundbreaking move is that some Nehalem CPUs will have a GPU integrated (Intel's version of "Fusion"). With an integrated memory controller, new interconnect, and potentially integrated graphics, Nehalem will obviously require a new socket.

Intel would not give any more detail, but it is clear that the GPU will not be high-end (that would require too much power); more likely it will be a kind of midrange (or even low-end depending on your perspective) solution. Intel would not confirm this, but it seems pretty clear to us that Xeon DP and desktop products will probably have an IMC that supports DDR3. Xeon MPs will probably have an IMC that supports registered FB-DIMMs with DDR3. Nehalem should first be available in the second half of 2008 as Intel talked about "production ramping in 2008, with full production in 2009".

Final Words

Continuing the trend started by the "new Intel", today we were given a ridiculous amount of information about Intel's coming microprocessor architectures. Obviously part of today's announcements were intended to pre-empt any excitement about AMD's Barcelona architecture, but Intel is doing the right thing. It's sharing a very forward looking roadmap with the public early on in order to rebuild trust and confidence, especially after what happened with NetBurst.

This is the exact approach we would like AMD to embrace as well, keep the public informed, especially if you have exciting things to talk about. We understand the desire to try and protect trade secrets, but with the complexity of modern processors and the amount of information that gets shared between partners, not to mention "corporate espionage", it seems likely that Intel and AMD already more or less know what their competitors are planning. Changing course late in product development is nearly impossible to accomplish, and especially when current products begin to lag behind the competition we would expect companies to try to garner interest by talking about the future.

Looking to the future, one thing that is clear is that multi-core solutions are truly becoming the norm. We still haven't managed to realize the potential of even dual core solutions with many applications (particularly games), and with quad core and octal core processors in the pipeline the need for software to become more multithreading-friendly is reaching a critical stage. The good news is that we're beginning to hear a lot more about multithreaded software engine designs, and we are even beginning to see some of the fruits of these labors.

Naturally, without any actual hardware test, it is impossible to say right now whether Intel or AMD will come out on top with their next-generation processors. Regardless of which company "wins", the best news is that it appears the cutthroat competition will continue for the time being. All you have to do is look at current processor prices to appreciate the importance of competition, and we're certainly looking forward to the day when quad core and higher systems fall into midrange and lower price brackets!

Penryn Enhancements, Continued
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  • sdsdv10 - Thursday, March 29, 2007 - link

    Yes, I agree early disclosure is a good thing, but let's clarify the "public" doesn't hate RAMBUS. Most of the "public" doesn't know who Rambus is or even care. The only ones who hate Rambus is a minority of tech geeks who can't move on.
  • feelingshorter - Wednesday, March 28, 2007 - link

    So Intel will finally use a IMC like AMD. Does that mean overclocking will be relatively flat across the board? If all the CPUs of the same stepping have the same IMC, then overclocks will be less motherboard dependent wont it? Or am I confusing IMC with something else? That also means all the chip manufactures will have to find new business. Although they can continue to manufacture motherboards, we've seen what happened to companies in the past when AMD decided to use IMC.
  • tuteja1986 - Thursday, March 29, 2007 - link

    Well we will have to wait till Q2 of 2008 to see if intel cliams are true or not. Till then my eyes lay on AMD's Barcelona architecture since its coming out this year and if AMD claims are right then it should be able to beat up a intel offering.
  • Locutus465 - Wednesday, March 28, 2007 - link

    Oh yeah, you hit the nail on the head... Much more important than the actual performance gains is the fact that neither company is going to be sititing on their laurals putting out bad or otherwise unexciting products out for the forseeable future.

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