Nehalem details spill through the Tubes

December 3, 2007 | 08:42

Tags: #4 #45nm #8 #cache #controller #cores #cpu #integrated #nehalem #quad

Companies: #intel

More Nehalem news has made its way onto the net recently, via Japanese site PC Watch Impress (translator required). Even if you can't read the Kanji, there are lots of pictures in the link above, which I highly recommend nosing over, showing how things are likely to work inside Nehalem.

The general jist of things is as follows:
  • Nehalem-EX, codenamed Beckton, will have eight cores but supports 16 threads because HyperThreading makes a return. Each pair of cores will have an amount of shared cache between them, then there will be a mahoosive 24MB of shared cache between them all - basically a Stoakley platform on single chip.

    The EX is designed for a multi-processor environment so this has QPI, or Quick Path Interconnect--Intel's alternative to HyperTransport--with four links at 4.8 or 6.4Gbps and an FB-DIMM2 quad-channel memory controller. All this is under the envelope of varying TDPs of 90W, 105W and 130W and the chips use a new LGA socket with 1567 pins, Socket-LS.

  • Quad-core, dual-socket (DP) Nehalem-EP, codenamed Gainestown will also have HyperThreading and 8MB of cache, triple channel DDR3 and two QPI links bundled in either 60, 80 or 130W TDP. It'll also have a new LGA socket, but this time with 1366 pins.

  • The quad-core, "extreme" performance CPU codenamed Bloomfield, will be identical to the DP parts above, but will be single socket only and have a single QPI link. This will also be on socket LGA1366. It is suggested to have a 270mm² die size, about the same as current Kentsfield’s 65nm 286mm² die, but it’ll have nearly 150m more transistors at 731m.

  • Quad-core, performance mainstream CPUs codenamed Lynnfield and Clarkfield, will have a lower clock and lower TDPs of 90W for desktop and 45/55W for mobile. A more normal dual-channel DDR3 is included here with the integrated memory controller, but instead of a QPI link it will include a PCI-Express 2.0 x16 slot and DMI link to a southbridge instead. It'll have a different socket, again - this time it's called LGA1160.

  • Dual-core chips will still be around next year, with new cores codenamed Havendale and Auburndale - these have HyperThreading, come with 4MB of shared cache and in addition to the integrated memory controller they have a graphics core that's talked to via an internal QPI. The memory controller is dual-channel DDR3, with a TDP of 35-45W for mobile and under 95W for desktop. Additionally, it will have a PCI-Express 2.0 x16 graphics lane included. Like above, it features an LGA1160 socket.

    Remember, all this is stemming from the single CPU socket! AMD processors have had an integrated memory controller since the Athlon 64 launched, but not until Fusion arrives in 2009 now that we'll see a similar CPU from the green team.

    These CPUs will be predominantly mobile or mainstream parts that require integrated graphics and not as much processing power.
Obviously integrating a single PCI-Express x16 lane into the north bridge limits the multi-GPU usage, but it also makes the interface with graphics card, CPU and memory a lot faster being on all one package. In comparison, the more enthusiast-orientated parts will have a separate chipset that handles all the PCI-Express stuff and will require a graphics card to negotiate an extra stop before getting main memory access - a criticism of AMD's current CPUs.

Unfortunately the CPU sockets have been split in two between more mainstream and enthusiast parts - my guess will be that Intel is creating a very niche segment with very few, but expensive CPUs in it. As Intel's flagship product, these parts will require you to buy three DDR3 DIMMs for tri-channel memory, and while we'd assume this to normally be just a bit of a marketing gimmick - remember that SLI or CrossFire will likely only be available on these CPUs as Bloomfield has a QPI to a separate north bridge, unless someone hacks multi-GPU into a "south bridge/MCP" to work with Lynnfield/Clarksfield, but then you're limiting traffic to the bandwidth of the DMI.

The CPU-GPU Havendale and Auburndale processors should feature in many notebooks and your low profile inexpensive PCs. Having a motherboard only need a simple south bridge with everything else on CPU should make things cheaper, but might also have a more restricted upgrade path. In addition, even though Intel has stated it is committed to making integrated graphics far better than it has been, because of the limitation in space and heat output from a single space, that might cause a significant restriction on what it can achieve.

We expect some serious performance out of these CPUs given the current climate, although we are slightly sceptical about the increase in pipeline length Nehalem will have, even if it is just in the low twenties. There's nothing to say that in just a year we'll suddenly all require a whole load more multi-threading capabilities either.

The Japanese website suggests that Bloomfield will be the first Nehalem available in Q4 2008, with the rest possibly arriving in 2009.

Personally, after writing this I'm actually quite concerned about Intel's positioning - I'm worried that now Intel is the current preferred product over AMD, it'll use this leverage to try and suck out as much cash from enthusiasts as possible, and not have them overclock lower parts, like the E6300, Q6600 etc, to perform like £700 CPUs. At the same time, it's also potentially limiting the availability of multi-GPU by its competitors by forcing the separate north bridge, which offers better performance, to potentially only be available onto Bloomfield CPUs. It seems all the cards are in Intel's hands to deal precisely how it wishes.

Discuss these rumours in the forums.
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