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Home » CPU
Core i5-750 and Core i7-870 Processors Review
Author: Gabriel Torres 129,755 views
Type: Reviews Last Updated: September 7, 2009
Page: 2 of 13
Introduction (Cont’d)

Another important difference between socket LGA1156 and socket LGA1366 processors is the presence of a x16 PCI Express 2.0 controller inside the CPU. This is the first time a CPU manufacturer does something like this; until now, the PCI Express 2.0 controller was embedded on the chipset. The 16 PCI Express lanes present in the CPU can be connected to one x16 PCI Express 2.0 slot truly working at x16 or to two x16 PCI Express 2.0 slots working at x8 each. This new feature should improve the practical bandwidth achieved by graphics cards.

Socket LGA1366 CPUs  talk to the external world (i.e., the chipset) through a bus called QuickPath Interconnect (QPI), which has the same goal as the HyperTransport bus used with AMD CPUs. For a detailed explanation on how QPI bus works, read our Everything You Need to Know About The QuickPath Interconnect (QPI) tutorial. The new socket LGA1156 CPUs, however, use the DMI (Digital Media Interface) bus to talk to the chipset, which is the interface previously used to make the connection between the north bridge and the south bridge chips on Intel chipsets. At a first look this solution may seem worse than using the QPI bus, because the DMI interface provides a maximum transfer rate of 2 GB/s while QPI provides a maximum transfer rate of 4.8 GB/s or 6.4 GB/s, depending on the CPU. However, since now the CPU talks directly to the main video card without using its external bus and without using the chipset, this solution seems adequate. Both QPI and DMI offer a lower bandwidth compared to Core 2 Duo and Core 2 Quad external bus (see table below). Keep in mind that on these CPUs the external bus is used to make the communication between the CPU, the memory and everything else, while on socket LGA1156 and 1366 CPUs the processor has a separated communication channel with the memory and now on socket LGA1156 the CPU has a separated channel to talk with the main video card as well.

An important difference between Core i5 and Core i7 is the presence of the Hyper-Threading technology on the high-end family. This technology emulates two processing cores per physical core. So with Core i7 CPUs the operating system recognizes eight processors, even though the CPU has “only” four cores.

Both Core i5 and Core i7 support Intel Turbo Boost technology, which is essentially an automatic overclocking made by the CPU when it “feels” that the program needs more processing power, feature not present on Core 2 Duo and Core 2 Quad family of processors. Another difference between the two generations is on the memory cache. Core 2 Duo and Core 2 Quad CPUs have only one L2 memory cache, which is shared by all cores, while Core i5 and Core i7 have individual L2 memory caches for each core plus a L3 memory cache that is shared by all cores.

On the tables below we compare the main specs from the CPUs we included in this review. Due to the short time we had to collect data for this review and publish it as soon as possible, we couldn’t add all the processors we wanted in this comparison – especially competitors from AMD. We included the two socket LGA1366 Core i7 we had and the comparison between Core i5-750 and Core i7-920 should be interesting, as both run internally at 2.66 GHz. For the socket LGA775 selection, we decided to include Core 2 Extreme QX 9770 because it is the fastest (and most expensive) Intel CPU based on Core microarchitecture. A Core 2 Duo E8400 was included to represent a mainstream dual-core CPU and a Core 2 Quad Q6600 was included to represent a mainstream quad-core CPU based on Core architecture.

CPU

Cores

HT

Internal Clock

Turbo Clock

QPI or FSB Clock

Base Clock

Core

Technology

TDP

Socket

Price

Core i5-750

4

No

2.66 GHz

3.20 GHz

2 GB/s

133 MHz

Lynnfield

45 nm

95 W

1156

USD 196

Core i7-870

4

Yes

2.93 GHz

3.60 GHz

2 GB/s

133 MHz

Lynnfield

45 nm

95 W

1156

USD 562

Core i7-920

4

Yes

2.66 GHz

2.93 GHz

4.8 GB/s

133 MHz

Bloomfield

45 nm

130 W

1366

USD 284

Core i7-965

4

Yes

3.20 GHz

3.46 GHz

6.4 GB/s

133 MHz

Bloomfield

45 nm

130 W

1366

USD 999

Core 2 Extreme QX9770

4

No

3.20 GHz

12.8 GB/s

400 MHz

Yorkfield

45 nm

136 W

775

USD 1,399

Core 2 Quad Q6600

4

No

2.4 GHz

8.5 GB/s

266 MHz

Kentsfield

65 nm

105 W

775

USD 183

Core 2 Duo E8400

2

No

3 GHz

10.6 GB/s

333 MHz

Wolfdale

45 nm

65 W

775

USD 163

TDP stands for Thermal Design Power which advises the user of the maximum amount of heat the CPU can dissipate. The CPU cooler must be capable of dissipating at least this amount of heat.

The prices listed are the official prices for distributors based on 1,000 quantities. The end-user price is higher than the prices listed.

CPU

L1 Cache

L2 Cache

L3 Cache

Memory Support

Memory Channels

Core i5-750

32 KB + 32 KB per core

256 KB per core

8 MB total

DDR3 up to 1333 MHz

Two

Core i7-870

32 KB + 32 KB per core

256 KB per core

8 MB total

DDR3 up to 1333 MHz

Two

Core i7-920

32 KB + 32 KB per core

256 KB per core

8 MB total

DDR3 up to 1066 MHz

Three

Core i7-965

32 KB + 32 KB per core

256 KB per core

8 MB total

DDR3 up to 1066 MHz

Three

Core 2 Extreme QX9770

32 KB + 32 KB per core

12 MB total

None

Depends on Chipset (Two is the norm)

Core 2 Quad Q6600

32 KB + 32 KB per core

8 MB total

None

Depends on Chipset (Two is the norm)

Core 2 Duo E8400

32 KB + 32 KB per core

6 MB total

None

Depends on Chipset (Two is the norm)

Our tests have a couple of known flaws. Socket LGA1366 Core i7 processors support triple-channel memory configuration, but we used them with dual-channel configuration, because otherwise we wouldn’t be able to match the amount of memory used with the other CPUs (e.g., to run them under triple channel we would need three 1 GB memory modules, making them to run with 3 GB RAM instead of 2 GB like the other CPUs). The second “problem” is that these CPUs can access memory only up to 1,066 MHz and with the other CPUs memory was working at 1,333 MHz. We could make all CPUs to access memory at 1,066 MHz, but then some people could complain that we didn’t run the new Core i5-750 and the new Core i7-870 at their maximum performance. It is hard to find a methodology that pleases everybody.

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