Architecture
The Core i7 860 is the entry level processor of the LGA 1156 i7s. The release price of $285 is about the same as what the i7 920 LGA 1366 processor has dropped too after a year since its release. The i7 860 only comes in the retail package which means it includes a cooler. I have yet to use a cooler supplied with a CPU, and I won’t here either, as the integrated memory controller adds additional heat to these processors. Stock coolers will get you by if you don’t do much else but read email and surf the net, I highly recommend a quality aftermarket cooler if you game or benchmark, and DO NOT use a stock cooler if you do any overclocking whatsoever.
So let’s look at the differences between the LGA 1156 and the LGA 1366 i7s. Most obvious of course is the number of socket pins, the new i7 has 210 less pins. And the pins on the LGA 1156 motherboards are every bit as fragile as the LGA 1366. The difference in pin number has mostly to do with the different memory controllers on the two systems. The physical size is very different also, the LGA 1156 die size is about 75% that of the LGA 1366.
That pretty much takes care of the simple stuff. The rest can seem a little complicated. First let me talk a little about the LGA 1366 before comparing it to the LGA 1156.
The LGA 1366 series was the first Intel series of processors to have an integrated memory controller. Traditionally, memory control was a Northbridge function as part of the GMCH (Graphics and Memory Controller Hub) connected to the CPU by the FSB (Front Side Bus).
In LGA 1366, the FSB was replaced by QPI (Quick Path Interconnect) which was much more efficient and double the bandwidth of the FSB (25.6GB/sec opposed to 1600mHz). The processor was interfaced to the NB and SB via QPI.
I/O functions in the LGA 1366 were taken care of by the IOH (I/O Hub) located in the NB. Actually, that is what Intel calls the NB in the X58 chipset, since MCH (Memory Controller Hub) doesn’t apply anymore. The I/O controller gets pretty hot in the X58 due to the way that QPI works.
Now for the LGA 1156. LGA 1156 also has an onboard memory controller, the primary difference between the two is LGA 1366 has three memory channels, LGA 1156 has two.
Rather than taking place in the GMCH, the LGA 1156 has on-processor PCI-E x16 for communication with the graphics cards. This totally eliminates the GMCH in the NB.
Quick Path is also eliminated in the LGA 1156, replaced by DMI (Direct Media Interface). DMI was already around, it is a modified PCI-E x4 1GB full duplex interface. Using DMI for interfacing the IOH with the CPU allows for a much lower speed IOH, which in turn allowed it to be located on the SB.
So let’s contemplate the above information for a second. If you were able to follow my poor explanation, you may now have realized that the NB has been totally eliminated by the LGA 1156 processors. The P55 chipset consists only of the SB, which makes cooling the motherboard much more simple. Intel has eliminated a major (hot!) chip and it’s heatsink, so building a motherboard costs less than before. And this has obviously been passed on to us, the consumers, a quick look at my favorite online retailer shows about a $100 difference in the average price of P55 motherboards as compared to X58 motherboards. And keep in mind that most of the X58 motherboards have been on the market for the better part of a year!
Other than the above differences, LGA 1156 processors have the same basic differences from earlier Intel processors as the LGA 1366 processors. Both i7s have separate 256Kb L2 caches for each of the four cores and an 8Mb L3 cache shared by all four cores. Both have a greatly improved CPU pipeline (explained in greater detail here).
The LGA 1156 i7 processors also have Hyper-Threading (four virtual cores that make the processor perform as if it had eight cores) as did the LGA 1366. If you were wondering, the basic architectural difference between the LGA 1156 i7, and the i5, is the lack of Hyper-Threading.
So all in all, the basic differences between the LGA 1156 i7 and the LGA 1366 i7 is the lack of a Northbridge and dual channel memory rather than triple channel.
