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Intel Core i7

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Template:Infobox CPU QPI Intel Core i7 is a family of three Intel Desktop x86-64 processors, the first processors released using the Intel Nehalem microarchitecture and the successor to the Intel Core 2 family. All three models are quad-core processors.[1] The Core i7 identifier applies to the initial family of processors[2][3] codenamed Bloomfield.[4] The moniker Core i7 does not have a deeper meaning, but continues the use of the successful Core brand.[5] Core i7 was created in Costa Rica [6] and officially launched on November 17, 2008. [7]

Features

Nehalem represents the largest architectural change in the Intel x86 family since the Pentium Pro in 1995. The Nehalem architecture has many new features. The ones that represent significant changes from the Core 2 include:

  • FSB is replaced by QuickPath interface. Motherboards must use a chipset that supports QuickPath. As of 17 November 2008, Intel, EVGA, ASUS, MSI, Gigabyte have all released X58, all supporting the i7's LGA1366 Socket interface.
  • On-die memory controller: the memory is directly connected to the processor.
  • Three channel memory: each channel can support one or two DDR3 DIMMs. Motherboards for Core i7 have four (3+1) or six DIMM slots instead of two or four, and DIMMs should be installed in sets of three, not two.
  • Support for DDR3 only.
  • Single-die device: all four cores, the memory controller, and all cache are on a single die.
  • "Turbo Boost" technology allows the cores to intelligently clock themselves to 133MHz or 266MHz over the design clock rate so long as the CPU's thermal requirements are still met. This mode isn't enabled when the CPU is manually over-clocked by the user.
  • Re-implemented Hyper-threading. Each of the four cores can process two threads simultaneously, so the processor appears to the OS as eight CPUs. This feature was present in the older NetBurst architecture but was dropped in Core.
  • On-die, shared, inclusive 8MB L3 cache.
  • Only one QuickPath interface: not intended for multi-processor motherboards.
  • 45nm process technology.
  • 731M transistors.
  • Sophisticated power management can place an unused core in a zero-power mode.

Drawbacks

  • The Core i7 or at least, any current motherboard for the Core i7 as of November 13, 2008 (two ASUS boards, two MSI boards, a DFi board, an ECS, an EVGA and the Intel DX58SO, gigabyte board -- data available from manufacturer website) does not support ECC memory.[citation needed] Some experts, such as Daniel Bernstein[8], recommend that systems lacking ECC support should be avoided unless occasional errors are acceptable. However, most users opt for non-ECC memory anyway.
  • As of 2008-11, DDR3 SDRAM costs significantly more per gigabyte than equivalent-bandwidth DDR2. [9]

Processors

  • The clock rates listed here are for normal mode. The clock rate on a single core can increase by up to 400MHz when the other cores are turned off.
  • The 965 XE has separate unlocked multipliers for memory and cores.
    • Memory bandwidths up to DDR3-2000 are possible, but not supported by Intel
    • Core clocks of up to 4GHz have been reported, but are not supported by Intel[10]
  • The processor has a Thermal Design Power of 130W and will slow itself down if this power is exceeded. This feature can be disabled from an option in most of the new motherboards' BIOS.[11]
  • Prices are per unit in lots of 1000 in USD
Core i7
Model[12] 		Process Cores
(Threads) 		Clock
(GHz) 		Price Cache Memory controller[13] QuickPath
Interface 		TDP
[11] 		Socket Release
date
920 45nm 4
(8) 		2.66 $284 256 KB L2/core
8 MB shared L3 		3xDDR3 800/1066 MHz 1x 4.8 GT/s 130W LGA1366 2008-11-17
940 2.93 $562
965 Extreme Edition 3.2 $999 1x 6.4 GT/s

Performance

File:IntelCorei7Extreme.png
Intel Core i7, Extreme Edition
File:Corei7.png
Intel Core i7

A 2.93 GHz Core i7 940 system has been used to run a 3DMark Vantage benchmark and gave a CPU score of 17,966.[14] The 2.66 GHz Core i7 920 scores 16,294. An earlier generation Core processor, 2.66 GHz Core 2 Quad Q9450, scores 11,131.[15]

AnandTech tested the Intel QuickPath Interconnect (4.8 GT/s version) and found the copy bandwidth using triple-channel 1066 MHz DDR3 was 12.0 GB/s. A 3.0 GHz Core 2 Quad system using dual-channel 1066 MHz DDR3 achieved 6.9 GB/s.[16]

Over-clocking will be possible with the 900 series and a motherboard equipped with the X58 chipset. In early October 2008, reports surfaced that it will not be possible to use "performance" DDR3 DIMMs that require voltages higher than 1.65v, because the integrated memory controller within the Core i7 will be damaged.[17] Some tests, however, have demonstrated that the voltage limit does not apply, like on a MSI board, and manufacturers can choose to bond CPU voltage to memory or not. By the end of that month, performance memory vendors had announced 1.65v DDR3 memory kits with clock rates up to 2GHz.

Some early articles suggested that i7's design is not ideal for gaming performance. In a test done on leaked hardware, a Core i7 940 compared to a QX9770 shows the Core i7 is slower than Yorkfield clock for clock in 2 while being faster in the other two. The difference in all cases is small, and is due to the significantly smaller sized L2 cache on the processor cores, with each core able to access its own 256 kB of L2 cache. In contrast, the most recent Yorkfields have up to 12 MB of L2 cache. To help compensate, the Core i7 also has a new L3 cache of 8 MB, shared among all four cores, similar to AMD's "Barcelona" processors.[18] However, more recent testing done on all clock rates of official hardware with final drivers and BIOS revisions show that Core i7 at the very least beats Yorkfield clock-for-clock, and in most cases exceeds it by an average of about 17%.[19]

In the single-threaded Super PI 1M test, a Core i7 920 running at 2.66 GHz finished the test in 15.36 seconds, while a QX9770 (3.2 GHz) did the test in 14.42 seconds[20], so the Core i7 executed 20% more instructions per clock cycle on this test.

The Core i7 has three memory channels, and the channel bandwidth can be selected by setting the memory multiplier. However, in early benchmarks, when the clock rate is set higher than a threshold (1333 for the 965XE) the processor will only access two memory channels simultaneously. A 965XE has higher memory throughput with 3xDDR3-1333 than with 3xDDR3-1600, and 2xDDR3-1600 has almost identical throughput to 3xDDR3-1600.[10]

Since the Core i7 is a quad-core processor, Hyperthreading cannot yield any performance improvement for application workloads with fewer than five simultaneous threads when all the cores are fully powered on, and some applications will suffer a performance degradation when hyperthreading is enabled.[21] Hyperthreading will provide its best improvement when the workload has eight or more simultaneous threads.

References

  1. ^ "Intel Details Upcoming New Processor Generations" (Press release). Intel Corporate. 2008-08-11.
  2. ^ "Meet the Bloggers". Intel Corporation. Retrieved 2008-08-11.
  3. ^ "Getting to the Core---Intel's new flagship client brand". Intel Corporation. Retrieved 2008-08-11.
  4. ^ "[Intel Roadmap update] Nehalem to enter mainstream market". ExpReview. 2008-06-10. Retrieved 2008-08-11.
  5. ^ "IDF Fall 2008: Intel un-retires Craig Barrett, AMD sets up anti-IDF camp". Tigervision Media. 2008-08-11. Retrieved 2008-08-11.
  6. ^ "Intel "Hecho En Costa Rica"". InsideCostaRica.com. 2008-11-19. Retrieved 2008-11-19.
  7. ^ "Intel Calls Core i7 World's Fastest, Sets Launch Date". PC Magazine. 2008-11-05. Retrieved 2008-11-05.
  8. ^ Bernstein's 2001 Web page
  9. ^ geizhals.at, a price comparison website for austria and germany
  10. ^ a b Novakovic, Nebojsa (2008-11-06). "Nehalem chugs along merrily at 4GHz with just a fan". the Inquirer. Retrieved 2008-11-07.
  11. ^ a b Angelini, Chris (2008-11-04). "Editor's Corner: Overclocking Core i7". Tom's Hardware. Retrieved 2008-11-08.
  12. ^ "Box codes". 2008-09-16.
  13. ^ "Tom's Hardware RAM multipliers". 2008-11-02. {{cite web}}: Check date values in: |date= (help)
  14. ^ Nguyen, Tuan (2008-07-09). "'Nehalem' 2.93 GHz Benches Revealed". Tom's Hardware.
  15. ^ "Tom's Hardware: Desktop CPU Charts Q3/2008: 3d Mark Vantage - CPU". Tom's Hardware!. 2008-11-05.
  16. ^ "Intel does it again". AnandTech. 2008-06-05.
  17. ^ Taylor, Paul (03 October 2008). "Performance RAM will damage your Nehalem". The Inquirer. {{cite web}}: Check date values in: |date= (help); Unknown parameter |access_date= ignored (help)
  18. ^ "Intel Core i7 940 in Real Test". UneIT. 2008-09-24.
  19. ^ Nelson, Carl (02 November 2008). "Intel Core i7 CPU Review". {{cite web}}: Check date values in: |date= (help); Unknown parameter |access_date= ignored (help); Unknown parameter |publishe= ignored (help)
  20. ^ "Intel Core i7 920 Tested". Yobeta.com. 2008-10-04.
  21. ^ Abi-Chahla, Fedy (October 14, 2008). "Intel Core i7 (Nehalem): Architecture By AMD?". Tom's Hardware. Retrieved 2008-10-14.
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