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What’s In A Name?

Intel Core i5 And Core i7: Intel’s Mainstream Magnum Opus
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With Core 2 Quad and Core 2 Duo, you had a general idea of what you were dealing with upfront. Adding a Q8000- or E7000-series designator wasn’t particularly descriptive, but at least there was one tangible identifier in there for the layman to digest.

When Intel introduced Core i7 last year, the fact that there was only one Nehalem-based desktop family made it easy to say “Core i7—yeah, high-end stuff,” regardless of whether you were actually talking about the $300 i7-920 or the $1,000 i7-965.

Core i7, Core i5, and Core 2 QuadCore i7, Core i5, and Core 2 Quad

Now you have Core i5 and another strain of Core i7; at this point the nomenclature is just jargon for everyone except for the power users who live and breathe this stuff. Let’s break it down in a neat little table, though.


Core i7 (LGA 1366)
Core i7 (LGA 1156)
Core i5
Core 2 Quad
Processor Interface
LGA 1366
LGA 1156
LGA 1156
LGA 775
Number of Cores
4
4
4
4
Turbo Boost
Yes
Yes
Yes
No
Hyper-Threading
Yes
Yes
No
No
L1 Cache
32KB/32KB per core
32KB/32KB per core
32KB/32KB per core
32KB/32KB per core
L2 Cache
256KB per core
256KB per core
256KB per core
Up to 12MB shared
L3 Cache
8MB shared
8MB shared
8MB shared
No
Memory Channels
3
2
2
2
Max. Memory Rate
DDR3-1066
DDR3-1333
DDR3-1333
DDR3-1600
Chipset
X58
P55
P55
X48
Price
$284-$999
$285-$555
$199
$163-$316


As you can see, Core i7 for LGA 1366 remains the enthusiast-class offering, sporting the most PCI Express 2.0 connectivity via Intel’s X58 Express chipset, up to three available channels of DDR3 memory support, Intel’s first generation of Turbo Boost, and Hyper-Threading.

Core i7-870Core i7-870Core i5-750Core i5-750

Core i7 for LGA 1156 integrates the PCI Express connectivity (albeit 16 lanes instead of 36), sheds one memory channel, incorporates an updated implementation of Turbo Boost, and maintains Hyper-Threading support.

Core i5 includes the same on-board PCI Express subsystem and dual-channel integrated memory controller. It employs Intel’s improved Turbo Boost (though it’s slightly less aggressive than i7’s). What it lacks, however, is Hyper-Threading—apparently a noteworthy-enough capability to turn an i7 into an i5. Of course, descending the stack also results in lower base clock rates.

The Making Of A Core i5/i7

Architecturally, most of what you get in a Core i5 or Core i7 processor is borrowed from technology already found in Intel’s LGA 1366-based Core i7 and Xeon 3500-series processors. The Lynnfield die is different from Bloomfield though, estimated at 774 million transistors packed into 296 square millimeters (versus 731 million in 263 millimeters for the first Core i7s). More than 400 million of those transistors make up the CPU's cache.

As with Bloomfield, Lynnfield is a monolithic design divided into four cores (execution pipelines, L1 data/instruction cache, TLBs) and the uncore (L3 cache, integrated PCI Express, the memory controller, QPI, and the PLLs). The power for these two “halves” remains separate, independently adjustable in your motherboard's BIOS.

Bloomfield: core vs. uncoreBloomfield: core vs. uncore

Each of the four cores retains its 32KB L1 data cache (still 8-way set-associative), 32KB L1 instruction cache (still 4-way set-associative), and 256KB L2 cache (you guessed it—still 8-way set associative). An inclusive 8MB L3 cache 16-way set-associative) should look familiar as well. 

With nothing really new to report in the cores themselves, we move to the uncore, where Intel has added PCI Express 2.0 connectivity, axed a single memory channel, dropping the total to two, and altered QPI.

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