Core i7 875K - It's Lynnfield

Core i7 875K - It's Lynnfield

The second processor reviewed in today's article  is the high-end Core i7 875 based on socket LGA1156 as well. Lynnfield based Core i5/7 series 700 and 800 have 774 million transistors all jammed into a die size of 296mm². Where Clarkdale (655K) is based on a 32nm fabrication, Lynnfield still has to cope with the 45nm fab node. Based off Nehalem chips this processor will pack 64KB of L1 cache and 256KB of L2 cache. Those are supplemented by a large pool of shared L3 cache, which in the case of the quad-core model is 8MB. A good number of things have changed in its architecture. The biggest being Quick Path, the move forwards to an integrated dual or triple-channel DDR3 memory controller allowing the product heaps of memory bandwidth and Hyper Threading (Pentium 4 era technology). The Nehalem family brings in some improvements which signal important changes in the Intel approach to CPU and system scaling and DRAM memory management. Let's walk through them.

Intel now has four processors in this range today:

• Core i5 750 [2.66 GHz]
• Core i7 860 [2.80 GHz]
• Core i7 870 [2.93 GHz]
• Core i7 875K [2.93 GHz] @ 342 USD

Some key features:

• Four x86 processing cores with support for HyperThreading technology
• Dual-channel DDR3 memory controller specified to run DDR3-1066 and DDR3-1333 modules
• Support for TurboBoost technology
• 32 KB instruction + 32 KB data L1 cache per core
• 256 KB L2 cache per core
• Large 8 MB L3 cache shared by all 4 cores

Intel has been shipping the Core i5 750, Core i7 860 and Core i7 870 for a while now, and the Core i7 875K starts shipping this week, with a clock-speed of 2.93GHz.

You might wonder, what are the differences between Bloomfield (socket 1366) based Core i7 processors and Lynnfield based Core i7 processors? Two things really, dual-channel memory support (not triple-channel) and another socket (1156). Like it or not, Lynnfield processors are definitely a small step back. But don't get scared just yet though, they are seriously fast.

• Core i5 750 maximum multiplier 20x133 = 2.66 GHz
• Core i7 860 maximum multiplier 21x133 = 2.80 GHz
• Core i7 870 maximum multiplier 22x133 = 2.93 GHz
• Core i7 875K maximum multiplier unlocked ??x133 = 2.93 GHz (Q3Z3)

 Turbo mode

Core i5 and Core i7 processors have something that is called 'Turbo mode'. Depending on CPU load one or more CPU cores will run above its advertised specification. Much like the initial Turbo mode introduced for Core i7, the new Lynnfield processors have Turbo mode as well. It changed a little as there are several (five) steps in which the Turbo mode will be utilized.

Very simply: if one CPU thread is used only one processor core will automatically overclock in this order, Core i5 655K to 3.46GHz, the i7 875K to 3.60GHz.

However look at the following image, if two threads are used on two cores, the Core i7 875K for example will then clock both cores at 3.4 GHz. And if there is massive CPU utilization on all four CPU cores, Turbo mode will still kick in at 3200 MHz (for the Core i7 875K) on all active CPU cores.

Anyway, you guys should know all this by now, let's have a look at the product and then start up some overclock sessions.