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Intel Core i5-661: A 32nm CPU with Integrated Graphics

Intel Core i5-661: A 32nm CPU with Integrated Graphics

January 4, 2010 by Lawrence Lee

Product Intel Core i5-661

LGA1156 Processor
Manufacturer Intel
MSRP US$196

To kick off 2010, Intel has released a new batch of Core i7, i5 and i3 processors,
codename Arrandale for laptops, and Clarkdale for desktops. These new CPUs are
rather interesting in that there are two chips on the same package: a small
dual core processor manufactured using their new 32mm fabrication process connected
internally with QPI to a larger 45nm chip that houses the memory controller and
an updated IGP that supports OpenGL 2.1, simply dubbed Intel GMA HD.



Clarkdale die image.

While quad core processors will continue to dominate the high-end desktop market,
there is still a strong case to be made for dual core chips. They are more affordable
(at equivalent clock speeds), use less energy and are thus easier to cool. And
though they have half the cores, higher clock speeds are more of a benefit for some
games and applications, not all of them. For the average Joe that doesn't spend hours encoding
video or manipulating high resolution images with advanced filters, a 3+ GHz
dual core CPU is often a better choice.

Comparison Table: Dual Core Core i5/i3 Desktop Processors
Model
Clock Speed
Turbo Speed
L3 Cache
TDP
Pricing*
Core i5-670
3.46 GHz
3.73 GHz
4MB
73W
$284
Core i5-661
3.33 GHz
3.60 GHz
4MB
87W
$196
Core i5-660
3.33 GHz
3.60 GHz
4MB
73W
$196
Core i5-650
3.20 GHz
3.46 GHz
4MB
73W
$176
Core i3-540
3.06 GHz
N/A
4MB
73W
$133
Core i3-530
2.93 GHz
N/A
4MB
73W
$113
* boxed price (1000 units)

The first six dual core LGA1156 processors have frequencies ranging from 2.93
GHz to 3.46 GHz with all models supporting hyper-threading so the operating
system will see 4 threads instead of 2. For the budget-conscious, the Core i3's
start at only $113 and the only major thing missing is the TurboBoost overclocking
feature. The Core i5-661 runs at 3.33GHz but with TurboBoost
enabled, overclocks to 3.60GHz when a demanding application is running that
can only use one core. The speed is bumped up to 3.46GHz when both cores are
active.



i5-6xx vs. i5-6x1.

The Core i5-661 is an unusual processor, in name and features.
Both AMD and Intel desktop chips typically have a '0' or '5' at the end of their
model numbers. The "1" indicates that the part in question has a higher
speed graphics core and accompanying TDP, and lacks a few of Intel's lesser
known technologies, the most notable being VT-d, which gives virtual machines
the ability to directly access peripherals on their host. Features like this
are usually only cut on lower-end parts, and the i5-661 is the only one of its
kind for now, so it's a very odd duck indeed, resembling a Core i3 with an overclocked
IGP.



CPU-Z screenshot: Core i5-661 at load with TurboBoost disabled.




Our Core i5-661 sample.

MOTHERBOARD

With the redesigned processor, new chipsets are required to take advantage
of GMA HD. The H55 Express is Intel's new mainstream LGA1156 chipset.



H55 chipset block diagram.



To test the Core i5-661, Intel shipped the processor with the DH55TC
budget mATX motherboard. The estimated street price for this board is
~US$100.



Like most Intel boards, the color scheme used is a soothing dark blue.
The board's layout is fairly standard and clean.



As a budget board, solid state capacitors are used for the VRM area only.
The board has only a single, small, aluminum chipset heatsink.



Back ports include VGA, DVI, and HDMI, however since the IGP has moved
onto Clarkdale processors, using a Lynnfield CPU with this board will
require the addition of a discrete graphics card.

TEST METHODOLOGY

Common Test Platform:

AMD AM3:

Intel LGA775:

Intel LGA1156:

  • Intel Core i5-750
    processor - 2.66GHz, 45nm, 95W
  • Intel Core i5-661 processor - 3.33GHz, 32nm, 87W
  • Intel
    DP55KG
    motherboard - P55 chipset (for Core i5-750)
  • Intel DH55TC motherboard - H55 chipset (for Core i5-661)
  • Thermalright
    MUX-120
    CPU cooler



Device listing (CPU test platform).

Measurement and Analysis Tools

  • CPU-Z
    to monitor CPU frequency and voltage.
  • CPUBurn
    processor stress software.
  • Prime95
    processor stress software.
  • ATITool
    artifact scanner to stress the integrated GPU.
  • FurMark
    stability test to stress the integrated GPU.
  • Cyberlink
    PowerDVD
    to play H.264/VC-1/Blu-ray video.
  • Eset NOD32 as
    an anti-virus benchmark.
  • WinRAR as an
    archiving benchmark.
  • iTunes
    an audio encoding benchmark.
  • TMPGEnc
    Xpress
    as a video encoding benchmark.
  • PCMark05
    as a general system benchmark.
  • 3DMark05
    as a 3D benchmark.
  • 3DMark06
    as a 3D benchmark.
  • Seasonic
    Power Angel
    AC power meter, used to measure the power consumption
    of the system.
  • Custom-built, four-channel variable DC power supply, used to power
    and regulate the CPU fan.

Estimating DC Power

The following power efficiency figures were obtained for the
Seasonic SS-400ET used in our test system:

Seasonic SS-400ET Test Results
DC Output (W)
AC Input (W)
Efficiency
21.2
32.0
66.3%
41.6
58.0
71.7%
60.2
78.0
77.1%
81.9
102.0
80.3%
104.7
128.0
81.8%
124.1
150.0
82.8%
145.2
175.0
83.0%
165.3
195.0
84.8%
193.2
227.0
85.1%
222.7
261.0
85.3%

This data is enough to give us a very good estimate of DC demand in our
test system. We extrapolate the DC power output from the measured AC power
input based on this data. We won't go through the math; it's easy enough
to figure out for yourself if you really want to.

Testing Procedures

Our IGP testing procedure is to run the system through a video test suite featuring
a variety of high definition clips. During playback, a CPU usage graph is created
by the Windows Task Manger for analysis to determine the average CPU usage.
High CPU usage is indicative of poor video decoding ability. If the video (and/or
audio) skips or freezes, we conclude the IGP (in conjunction with the processor)
is inadequate to decompress the clip properly.

Our CPU testing procedure is designed to determine the overall system power
consumption at various states (measured using a Seasonic Power Angel). To stress
CPUs we use Prime95 (large FFTs setting) or CPUBurn, whichever produces the
higher power draw. We also perform a short series of benchmarks featuring real-world
timed tests and synthetics detailed below.

Cool'n'Quiet and/or Intel SpeedStep were enabled (unless otherwise noted).
The following features/services were disabled during testing to prevent spikes
in CPU/HDD usage that are typical of fresh Vista installations:

  • Windows Sidebar
  • Indexing
  • Superfetch

CPU Benchmark Details

  • Eset NOD32: In-depth virus scan of a folder containing 32 files of
    varying size with many of them being file RAR and ZIP archives.
  • WinRAR: Archive creation with a folder containing 68 files of varying
    size (less than 50MB).
  • iTunes: Conversion of an MP3 file to AAC (256kbps).
  • TMPGEnc Xpress: Encoding a 1-minute long XVID AVI file to VC-1 (1280x720,
    30fps, 20mbps).

Video Test Suite



1080p | 24fps | ~10mbps
H.264:
Rush Hour 3 Trailer 1
is a H.264 encoded clip inside an Apple
Quicktime container.





1080p | 24fps | ~8mbps
WMV-HD:
Coral Reef Adventure Trailer
is encoded in VC-1 using the
WMV3 codec commonly recognized by the "WMV-HD" moniker.




1080p | 24fps | ~19mbps
VC-1: Drag Race is a recording of a scene from
network television re-encoded with TMPGEnc using the WVC1 codec, a
more demanding VC-1 codec.




1080p | 24fps | ~33mbps
Blu-ray: Disturbia is a short section (chapter
4) of the Blu-ray version of Disturbia, the motion picture, played
directly off the Blu-ray disc. It is encoded with H.264/AVC.




1080p | 24fps | ~36mbps
Blu-ray: Becoming Jane is a short section (chapter
7) of the Blu-ray version of Becoming Jane, the motion picture, played
directly off the Blu-ray disc. It is encoded with VC-1.

IGP Test Results

To evaluate the performance of Intel GMA HD graphics, we setup the i5-661 in
our standard motherboard test platform featuring a notebook hard drive, Blu-ray
drive, and Seasonic power supply. Our test results for Intel's previous flagship
IGP, GMA X4500HD were obtained using a 2.53GHz Core 2 Duo E7200. To make it
a more fair battle, we tested the i5-661 underclocked to 2.26GHz by lowering
the CPU's multiplier to 17x in addition to stock speed.

Video Playback
Test State
Core i5-661 @ 3.33GHz
(Stock)
Core i5-661 @ 2.26GHz
(Underclocked)
Avg.

CPU
System Power (DC)
Avg.

CPU
System Power (DC)
Rush Hour

(H.264)
3%
31W
17%
31W
Coral Reef

(WMV-HD)
8%
31W
10%
31W
Drag Race

(VC-1)
13%
35W
16%
34W
Disturbia

(Blu-ray H.264)
28%
43W
39%
40W
Becoming Jane

(Blu-ray VC-1)
13%
39W
16%
38W
TurboBoost disabled during video playback testing.

Like most modern IGPs, Intel's GMA HD had no problem rendering our video test
suite with low CPU utilization playing both H.264 and VC-1 content with the
CPU at stock speeds. Even underclocked by almost a third, playback was smooth,
though H.264 playback was more reliant on CPU resources than we usually see
when using Nvidia or ATI graphics. Power consumption was very low during playback.

Video Playback: GMA X4500HD vs. GMA HD
Test State
E7200 @ 2.53GHz (Intel DG45FC)
Core i5-661 @ 2.26GHz (Intel DH55TC)
Avg.

CPU
System Power (DC)
Avg.

CPU
System Power (DC)
Rush Hour

(H.264)
30%
29W
17%
31W
Coral Reef

(WMV-HD)
25%
30W
10%
31W
Drag Race

(VC-1)
40%
33W
16%
34W

Despite a 266MHz disadvantage in processor clock speed, the i5-661's GMA HD
required significantly less CPU assistance to play HD video compared to the
GMA X4500HD paired with a Core 2 Duo E7200. Either the IGP is more efficient
or the i5 processor is much faster clock for clock (or a combination of the
two). Power consumption was similar on both platforms.

3D Performance: Futuremark Comparison
Motherboard
Graphics
3DMark05
3DMark06
Asus P5Q-EM

(C2D E7200)
X4500HD
1708
1092
MSI KA760GM

(X2 4850e)
HD 3000
2289
1049
Gigabyte MA78GM-2SH

(X2 4850e)
HD 3200
2293
1116
Intel DH55TC

(Core i5-661 @ 2.26GHz)
GMA HD
3179
1676
Intel DH55TC

(Core i5-661)
GMA HD
3215
1688
Zotac GeForce 9300-ITX (C2D E7200)
GF9300
3522
1797
Asus M4A785TD-V

(X3 720 BE)
HD 4200 (Sideport)
4095
1789
Asus M4A78T-E

(X3 720 BE)
HD 3300 (Sideport)
4884
2205
System configuration: 2GB of RAM, 256MB of VRAM
assigned (128MB for motherboards with 128MB of Sideport memory).

GMA HD is also a faster IGP in 3D performance, with a hefty improvement onver
X4500HD in both 3DMark05 and 3DMark06. Its scores put it close to the GeForce
9300, but still aways off from the Sideport equipped HD 4200/3300 for AM3. For
older games at lower resolutions, it should be sufficient. Note that the i5-661's
GPU has a 900MHz clock speed while the other Clarkdales have to suffice with
733MHz.

CPU/VRM Power Consumption

To get an idea of how much power the CPU actually requires, we measured the
current (through a 0.01 ohm shunt resistor) and voltage at the ATX12V connector in various CPU load states. This allows us to calculate the power demanded by the CPU and the board's VRM (DC-DC converter).

DC Power Consumption
Test State
Core i5-661 @ 3.33GHz

(Stock)
Core i5-661 @ 2.26GHz (Underclocked)
System
CPU + VRM
Diff.
System
CPU + VRM
Diff.
Idle
18W
5.3W
12.7W
18W
5.2W
12.8W
CPU Load
60W
46.0W
14.0W
45W
32.4W
12.6W
CPU + GPU

Load
67W
51.2W
15.8W
54W
39.0W
15.0W
CPU Load (Turbo)
63W
48.0W
15.0W
N/A
CPU Load + GPU Load (Turbo)
69W
52.7W
16.3W
N/A
CPU + VRM power measured from the ATX12V connector
(combined DC draw of VRMs and CPU).

By our measurements, our i5-661 sample used 5.3W when idle and up to 46.0W
when stressing the CPU with Prime95, with an indeterminate amount lost to VRM
inefficiency. The addition of FurMark's GPU stability test resulted in an additional
5.2W draw.

Between 13W and 16W was used by the rest of the system which consisted of the
motherboard, two sticks of memory, a notebook hard drive, idle Blu-ray drive,
keyboard and mouse.

System Power Consumption Comparison

To compare the Core i5-661 to other processors we've tested, we changed the
hardware to match our CPU testing platform, swapping the notebook hard drive
for a Velociraptor and using a GeForce 9400GT rather than integrated graphics.

Test Results: System Power Consumption (DC)
Processor
Idle
VC-1

Playback
CPU

Load
C2Q Q9550
47W
57W
115W
Core i5-750
37W
55W
107W
Core i5-661

(Turbo)
31W
45W
79W
Core i5-661
31W
45W
78W
C2D E7200
41W
50W
69W
X4 955 BE
56W
79W
171W
X3 720 BE
58W
77W
127W
X2 550 BE
48W
67W
106W

Back in September we reviewed the Core i5-750 and i7-860 Lynnfield quad core
processors and found them to very energy efficient. The i5-661, utilizing a
smaller manufacturing process and half the cores is even more thrifty when it
comes to power draw. Power consumption was 10W less than the Core 2 Duo E7200
when idle and only 10W more on full CPU load. AMD's fastest dual core, the X2
550 Black Edition, an 80W chip, was off the mark by 20~30W.

CPU Performance

Test Results: Benchmarks
Processor
NOD32
WinRAR
iTunes
TMPGEnc
PCMark05
C2Q Q9550
2:31
2:59
3:33
3:14
8760
Core i5-750
2:31
2:38
3:48
3:21
8390
Core i5-661 (Turbo)
2:03
3:30
3:03
3:32
9342
Core i5-661
2:08
3:35
3:10
3:39
9220
C2D E7200
2:47
3:34
4:00
6:10
7057
X4 955 BE
2:27
3:05
4:34
2:52
9004
X2 550 BE
2:34
3:09
4:44
4:54
7217
X3 720 BE
2:47
3:16
5:13
5:08
7738

Our timed benchmark tests were chosen to simulate average use, thus the i5-661
performed very well compared to the competition, winning in an anti-virus scanning
race using NOD32, and an audio encoding test using iTunes. Surprisingly, the
i5-661 came close to catching its similarly priced quad core cousin, the i5-750,
when video encoding using TMPGEnc, test which favors quad cores. Even a task
using multiple threads is not a sure-fire win for a quad core over a dual core.

Benchmark Power Consumption

Average System Benchmark Power Consumption (DC)
Processor
NOD32
WinRAR
iTunes
TMPGEnc
C2Q Q9550
66W
77W
70W
92W
Core i5-750
57W
61W
57W
88W
Core i5-750 (Undervolted)
54W
53W
56W
76W
Core i5-661 (Turbo)
52W
53W
55W
70W
Core i5-661
49W
50W
53W
69W
X4 955 BE
105W
105W
113W
138W
X3 720 BE
91W
90W
96W
107W
X2 550 BE
85W
85W
87W
96W
Total System Benchmark Power Consumption (watt-hours,
DC)
Test State
NOD32
WinRAR
iTunes
TMPGEnc
Total
Q9550
2.77
3.83
4.14
4.96
15.70
i5-750
2.39
2.68
3.61
4.91
13.59
i5-750 (Undervolted)
2.27
2.33
3.55
4.24
12.38
Core i5-661 (Turbo)
1.78
3.09
2.80
4.12
11.79
Core i5-661
1.74
2.99
2.80
4.20
11.72
X4 955 BE
4.29
5.40
8.60
6.59
24.88
X3 720 BE
4.22
4.90
8.35
9.15
26.62
X2 550 BE
3.64
4.46
6.86
7.84
22.80

When we combine the i5-661's strong performance in our timed benchmarks with
the average system power consumption during these tests, we find that it not
only finishes tasks quickly, but does so using less total power than any processor
we've tested to date. In terms of total watt-hours used for our entire test
suite, the i5-661 platform was ahead of the i5-750 by 14% and 5% when the i5-750
was undervolted to its minimum stable voltage.

Thermals

Temperatures
Sensor
Avg. Core
Chipset
VRMs
Core i5-661
41°C
39°C
39~44°C
Core i5-750
51°C
N/A
Core i7-870
53°C
Thermalright MUX-120 with stock fan @ 5.6V (900 RPM).

Ambient temperature: 22°C.

The average core temperature reported by SpeedFan stabilized at 41°C after
10~15 minutes on full CPU load, about 10°C lower than its quad core cousins.
The Thermalright MUX-120 heatsink used during testing was cool to the touch
even when the processor was stressed to the limit. Board temperatures were also
excellent with the VRMs around the CPU socket staying below 45°C and the
single chipset heatsink never passing 40°C at its hottest point, as measured
by an IR thermometer.

Motherboard Impressions

Budget Intel boards typically have very restrictive controls in the BIOS and
the DH55TC is no exception. The BIOS lacked controls for memory speed and did
not allow any voltage modification. In addition, TurboBoost could not be customized;
only an on/off toggle was provided.

As for compatibility, neither the Core i5-750 or i7-870 would POST in the DH55TC,
even with the latest BIOS from Intel. The DH55TC claims support for i7, i5,
and i3 on the box, so in theory it should work, if not now, then in the future.
The i5-661 would not work in our older DP55KG LGA1156 motherboard either.

FINAL THOUGHTS

The Core i5-661 is more than just a dual core version of the Lynnfield core
processor. A die-shrink from 45nm to 32nm gave Intel
the space to fit both a dual core processor and their latest onboard graphics
chip, GMA HD, onto the same package. This combination is very energy efficient,
rivaling the power consumption of a low speed Core 2 Duo, despite the Core i5-661's
much higher clock speed and overall performance.

GMA HD is a marked improvement over GMA X4500HD, rendering HD video using significantly
fewer CPU cycles and delivering much better 3D performance. Regarding the latter,
it should be noted that the GPU core of the i5-661 has a higher operating frequency
than the version of GMA HD found on the rest of the Clarkdale lineup. Even with
this advantage, it still trails behind AMD's HD 3300/4200 with Sideport memory. Still,
with either CPU/chipset, if you play even 3~4 year old games at the typical native resolution
of a modern widescreen LCD monitor, you will probably need a 'real' video card
to get decent framerates and image quality.

The Core i5-661's of whether the equivalently priced quad core Core i5-750 is superior. If you're a heavy multi-tasker or often use demanding applications that can take advantage of four cores like some video encoders, professional image editing software, and games, then the i5-750 is the better
candidate. However, if a program doesn't scale that well with multiple cores,
the higher clock speed of the i5-661 can give the i5-750 a run for its money.
For example, in our TMPGEnc video encoding test, the i5-661 finished only 5%
slower than the i5-750.

If you're a more casual user but you still value snappy performance, a dual core like the i5-661 is an excellent choice, particularly if
you have no need for discrete graphics. In many instances the higher clock speed
is actually more useful. In addition, the i5-661 is very energy efficient and
runs fairly cool, so you don't need an enormous, expensive heatsink/fan
to make it a quiet computing experience. The 6x0 series should run even cooler
as they utilize a slightly slower version of GMA HD; Intel lists their TDPs
at 73W vs. 87W for the i5-661. In summary, the Core i5-661 is a significant landmark in Intel's long stream of processors.

* * *

Articles of Related Interest

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Quad Cores


Intel's LGA1156 and Lynnfield
core


Intel Q9550S: A Greener Quad Core?

AMD Phenom II X2 550 BE & Athlon
II X2 250


AMD Phenom II X4 955 Black Edition for
AM3

* * *

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