THE RUMORS AND bits about Intel’s next generation core, Sandy Bridge, are starting to come out here and there, but several big chunks have still not been outed. Here are a few of them.
The first and biggest isn’t immediately apparent, but it becomes a little more obvious in the die shot below, taken from here. Several people who are much better at picking out chip structures have pointed out that the chip has a ring bus just like it’s older brother, Becton.
Die shot from IDF 2009
It is pretty clear that four cores do not need a ring bus. Intel has Nehalem’s at four cores, Westmere’s are slated for six, AMD’s Barcelona and Shanghai are at four, and its Istanbul is at six. While Intel could have gotten away with eight cores on Becton without a ring bus, the added uncore bits probably made it worth the additional effort.
That is the basis for a lot of interesting things hinted at by Intel’s increasing talk of modularity. Sandy Bridge does not need the ring bus, but it brings two things onto the die itself that probably do, graphics and PCIe. If you look at both die shots, the lower left corner is blanked out, and that is where the PCIe controllers would be. Llano has four PCIe controllers on die, but we don’t think Sandy Bridge will have nearly that many for the low end parts.
Having a ring bus means that Intel can add or subtract features with much more ease than doing things the ‘old way’. Instead of having to do most of the heavy lifting on interconnects again for a new variant or core count, they can just add a ring stop.
The same goes for uncore features, you can add a GPU, PCIe controller, memory controller, or likely even cache with with a fair bit of ease. If it was even possible with the older chips, it took a lot more time and effort. That is where Sandy Bridge will likely shine, flexibility. Intel will be able to make more dies for more markets with a lot less cost, and niches that were not considered before are now within reach. Dare we dream of an i6 or something with more than 5 stars?
Intel is also starting to not fear outsiders like it did before. It was dragged into opening Atom, feet first, kicking and screaming all the way, but it did that. While the initiative may have fizzled out, there is no doubt that Intel learned quite a bit from the experience. It looks like Intel could open up Sandy Bridge, or possibly Ivy Bridge to external IP, should it be accompanied by a large enough check.
The last bit is something that most people won’t think is a big deal, but it is quite possibly the biggest bang of the new chip. Intel is going to rearrange the internal architecture of Sandy Bridge to an extent that insiders tell us hasn’t really been done since the Pentium Pro back in the middle ages. The precise details are very hazy, but signs point to much greater flexibility, especially in terms of memory operations.
All in all, Sandy Bridge is going to be quite a change from what we see today. Integrated GPUs and PCIe lanes are the obvious bits that everyone will point to, but the big changes are under the hood. The bus is new, the microarchitecture is very different, and the ability to add and subtract bits is unprecedented on a consumer x86 chip. It will be quite interesting, and its successor, Ivy Bridge will likely exploit the potential to a much greater extent.S|A