New Processor: Core i7

Since Core i7 belongs to the new processor generation using Nehalem microarchitecture, we should start with listing all the innovations it will boast. Among the key peculiarities of the new CPU we absolutely have to point out the following:

• Native quad-core structure. Single processor die contains four cores with 256KB L2 cache each and a shared L3 cache for all of them.
• Quad Pumped Bus processor bus has been replaced with new serial interface aka QuickPath with point-to-point topology that may be used not only to connect the CPU and the chipset but also to connect processors with one another.
• Memory controller built into the CPU supports triple-channel DDR3 SDRAM. Each channel can work with two unbuffered DIMM modules.
• There is SMT (Simultaneous Multithreading) technology similar to Hyper-Threading technology. It allows each Core i7 core to process two computational threads simultaneously, so the operating system sees the CPU as an 8-core one.
• 8MB shared L3 cache.
• Integrated PCU microcontroller that independently adjusts voltages and core frequencies and can automatically overclock some cores when others aren’t loaded too heavily.
• New SSE4.2 instructions support.
• Core i7 is manufactured with 45nm process, consists of 731 mln transistors and has 263sq.mm die.

We should also keep in mind the microarchitectural improvements we have already discussed in our special dedicated article. Here we would like to say that there is nothing revolutionary about all these microarchitectural innovations and they mostly result from optimizations of the existing Core microarchitecture for work with SMT technology. All other innovations that come to desktop platforms together with Core i7 processors deal with the platform as a whole.

That is why no wonder that Core i7 processors differ from their predecessors not only on the inside, but also on the outside. New CPUs use LGA1366 processor socket that is larger and has more pins than the common LGA775 socket.

The processor has also become bigger. And unlike its predecessors, it is rectangular and not square.

The triple-channel memory controller must be the reason for adding more pins, because before that it used to be in the chipset North Bridge of Intel systems.

There will be three desktop Core i7 models available:

As you can see from the table above, the clock speeds of the new processors are not much different from the clock frequencies of their predecessors from Core 2 Quad family. And it means that the new generation processors will get their performance advantage from architectural solutions and new technologies.

As for the typical heat dissipation, Core i7 has higher TDP than Core 2 Quad processors. However, the top quad-core models on Core microarchitecture that belong to the Extreme Edition family have 136W TDP. It is quite logical that Core i7 doesn’t have any qualitative changes in the heat dissipation aspect: Nehalem microarchitecture didn’t get that far away from Core, and the manufacturing process used for Core i7 production remained completely the same.

Nevertheless, Intel decided that the old cooling solutions may not be used with the new processors and changed the distance between the cooler retention holes. They may have done it to encourage users to go for more efficient cooling solutions. You can tell by the cooler that arrived into our lab together with the test CPU sample. Before, the coolers for Core 2 processors used to feature aluminum heatsinks with copper core. Now half of the heatsink fins are also made of solid copper. The fins have become thinner and there are more of them; besides, the heatsink diameter is considerably larger now. However, to be fair we have to say that the fan on this cooler rotates with much lower speed ensuring comfortable acoustics.

The operating system sees Core i7 processors with enabled SMT technology as 8-core CPUs. Half of these cores are “virtual”, but Windows Vista doesn’t recognize this fact in any way.

The latest versions of diagnostic utilities detect Core i7 processor characteristics just fine.

Here I have to make an important point regarding the bus frequency of 133MHz detected by CPU-Z. The thing is that Intel decided to give up front side bus in its classical form in their new Core i7 processors, just like AMD did. In this case 133MHz frequency is the clock generator frequency used to form all other frequencies. For example, the CPU frequency is derived from this frequency multiplied by clock multiplier. The memory bus frequency is calculated the same way, only a different list of multipliers is used there. QPI interface connecting the CPU with the chipset North Bridge also uses this frequency and its own multiplier.

Just like in the previous CPU modes, processor clock frequency multiplier will be locked. The only exception will be Core i7-965 Extreme Edition model with an unlocked multiplier.

There will be several multipliers Core i7 processors will have for the memory bus frequency. For example, the Core i7-965 we tested in our lab offered to choose from 6x, 8x, 10x and 12x, which means that it supports DDR3-800/1067/133/1600 SDRAM.

The situation with QPI interface frequency is similar. It works at 3.2GHz in Core i7-965 Extreme Edition, while in Core i7-940 and i7-920 its frequency has been lowered to 2.4GHz.

Our Core i7-965 Extreme Edition sample is of C0 stepping, as you can see from the screenshot above. It is the final number that will be used for mass production CPUs. Our CPU had 1.2V Vcore, which is quite normal for a processor manufactured with 45nm process.