techpreview2012 sandybridgeedie big Intels Core i7 3820 and its compact die   truly cheaper Socket 2011?

While the Core i7 3960X was based on an 8-core die with 2 cores disabled, the just announced entry level Socket 2011 CPU, the Core i7 3820, is based on a different die. Intel will also offer 4-core Xeons based on the same smaller die. Any implications?

Good news is that the Socket 2011 platform entry just become a whole lot cheaper for the average enthusiast. At some 400 Singapore dollars apiece in the retail, the brand new Intel Core i7 3820 lets you combine it with an affordable entry level ATX X79 mobo, 4 sticks of DDR3-1333 Value RAM and, say, Radeon HD7770 GPU to make a roughly S$1,000 class basic kit before shopping for the enclosure and storage. Not bad at all!



What enabled that drastic CPU price drop, though? Just disabling more cores off the huge 8-core die doesn't make sense, especially since Intel's yields on these chips are improving as the subsequent steppings come out – C2 is the one to see this month, for instance. Intel may – and of course will – sell more of these as true 8-core Xeon E5's at upwards of one grand apiece, anyway.



Why not then just stick with the Socket 1155 4-core Sandy Bridge i7-2700K and its Xeon E3 equivalents? Well, there is a nice missing sweet spot in the market for both desktop and workstation/server users who don't need that many cores yet benefit from huge memory bandwidth & capacity given by the quad DDR3 channels, and also can use those 40 PCIe v3 lanes per socket. No Socket 1155 CPUs can provide that.



So, yes, Intel did produce a separate die which is, at roughly two thirds the total size of the big 8-core one, containing everything the big one has, except that the total core and cache count is halved, at 4 cores (8 threads) and 10 MB L3, all shared over a ring bus which, with only half the cores and caches in place, is now a little shorter for the round trip, reducing the internal latencies oh so slightly as well. Why not just 50% of the big die? Simple: the memory controller, the PCIe links, as well as the dual-link QPI, used in the dual socket Xeon E5 flavour, are still all the same, taking the same die area as well. Of course, this smaller die, with lower TDP and less heat to create, is also less demanding on the cooling.



The impact of the new entry? I feel this could be looked in two ways: one, it is a more attractive buy right now for any high end user wanting more and faster RAM and multi-GPU expandability without clunky PCIe bridges like the Lucid Hydra/Nvidia NF200 board over-heaters, for instance. The value for money, looking at the total system costs, definitely beats the Z68 Sandy Bridge LGA1155 platforms in this department. Of course, this changes if you're hell bent on waiting for the very first Ivy Bridge desktops sometime in April.



The other impact? It can bulldoze the Bulldozer, to put it that way. This processor, placed squarely in the AMD FX-8150 pricing territory, but with somewhat better CPU performance, and memory and I/O superiority to boot, makes any consideration of the current Bulldozer CPUs moot. AMD has to come out with Vishera processors as soon as possible, else Llano and the upcoming Trinity would remain the only competitive (in their own segments of course) offerings that AMD can place on the destkop.



Last but not least, the dual socket Xeon E5 version of this CPU, which is coming, and I saw it, will be loved by workstation and server users who need very high per-core performance but not too many cores, and yet worry about money grabbing per-core licensing policies of some server and workstation software vendors. After all, a pair of these would still have 8 fast cores total, plus 8 memory channels and 80 PCIe v3 lanes, truly lovely for a data mining machine on your desk, for instance…



It would be interesting to see if Intel will continue the same approach with the 10-core Socket 2011 Ivy Bridge EP processors sometime around the end of this year. One can't exactly cut a 10-core die in half easily, so, if they elect to continue this way, a 6-core cut-down die is more likely, at least to keep some differential vs the 4-core LGA1155 one, I assume.



In summary, a good move that lets Intel cover every price point from low end Core i3 to high end Xeons with just 4 dies: two LGA1155 (2-core and 4-core) and two LGA2011 (4-core and 8-core), all with likely leadership offering. And then comes the Haswell…