Intel markets the Q9550S quad core processor as an energy efficient variant of the Q9550. Our comparison seeks to answer two basic questions: Is the Q9550S’ power savings enough to justify its much higher price, and how does it compare to an undervolted Q9550?
June 22, 2009 by Lawrence Lee
Product | Intel Core 2 Quad Q9550S LGA775 Processor |
Manufacturer | Intel |
Street Price | US$335~$360 |
The high-end desktop processor market is saturated with products
that use a lot of energy. The fastest, Intel’s Core
i7s, all have thermal envelopes of 130W. AMD’s highest-clocked Phenom II quad
cores are rated for 125W, while most Intel
Core 2 Quads are rated for 95W. Intel is in a enviable position with a sizable
lead in performance at the very top, and energy efficient alternatives to rival
the best AMD has to offer.
Enter Intel’s Q9550S, Q9400S, Q8400S, and Q8200S, 65W variants of some of the
existing Core 2 Quad line. Rather than ramp up the performance of their Core
2 Quads (which would eat into their Core i7 and future Core i5 profits), Intel
has taken a page from AMD’s book, releasing more energy efficient chips.
AMD brands their energy efficient chips with an “E” at the end of
their model numbers, while Intel has decided to use “S.”
Comparison Table: Current Intel Core 2 Quad Lineup | |||||
Model | Clock Speed | Total L2 Cache | TDP | Mfg. Price | Best Online Price |
Q9650 | 3.00 GHz | 12MB | 95W | $316 | $320 |
Q9550S | 2.83 GHz | 12MB | 65W | $320 | $335 |
Q9550 | 2.83 GHz | 12MB | 95W | $266 | $220 |
Q9400S | 2.66 GHz | 6MB | 65W | $277 | $287 |
Q9400 | 2.66 GHz | 6MB | 95W | $213 | $214 |
Q8400S | 2.66 GHz | 4MB | 65W | $245 | N/A |
Q8400 | 2.66 GHz | 4MB | 95W | $183 | $174 |
Q8300 | 2.50 GHz | 4MB | 95W | $183 | $190 |
Q8200S | 2.33 GHz | 4MB | 65W | $183 | $236 |
Q8200 | 2.33 GHz | 4MB | 95W | $163 | $160 |
Pricing according to Intel’s Processor Price List and SPCR/Pricegrabber as of June 18 |
A 30W drop in power is nothing to sneeze at, especially for a high performance
chip like the Q9550 that’s likely to be put to good use on demanding applications.
Lower power consumption has obvious benefits, namely a reduction in operating
cost, but from silent computing perspective, a lower power processor puts out
less heat, making it easier to cool quietly. A 65W Core 2 Quad would be a better
choice for a small form factor system where performance
cannot be sacrificed yet cooling is not optimal. The “S” versions do come with a heavy price
premium, though. Currently, the slower model S processors
retail for $75 more than their 95W counterparts. For the Q9550S, the difference
is $115.
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Operating Voltage
Rather than tweaking processor design to yield a more energy efficient chip,
it is likely the “S” line are simply standard Core 2 Quads capable
of operating at lower voltages. They could be easily identified, plucked off
the assembly line and binned separately. Binning is an age-old practise that long precedes CPU manufacturing. Apples from the same orchard, for examples, have been binned into different grades, going back many centuries to when they were first grown for sale or trade.
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The Q9550S sample from Intel will be compared
primarily to a recent retail sample Q9550. Our Q9550S sample runs
at 1.144V according to CPU-Z, 64 mV less than our Q9550 sample.
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With SpeedStep in effect, both processors run at the same voltage when idle.
TEST METHODOLOGY
Common Test Platform:
- Zerotherm Zen FZ120
CPU cooler with Nexus 120mm fan - Corsair
XMS3 DHX memory – 2x2GB, DDR3-1600 @ 1333MHz, 9-9-9-24 - Asus EN9400GT Silent Edition
graphics card – 512MB - Western Digital VelociRaptor
hard drive – 300 GB, 10,000 RPM, 16MB cache, SATA - Seasonic
SS-400ET ATX power supply - Microsoft
Windows Vista SP1 operating system – Home Premium, 32-bit - nVidia
Forceware 182.50 graphics driver
Intel:
- Intel
Core 2 Extreme QX9650 processor – 3.0 GHz, 45nm, 125W - Intel
Core 2 Quad Q9550S processor – 2.83 GHz, 45nm, 65W - Intel
Core 2 Quad Q9550 processor – 2.83 GHz, 45nm, 95W - Asus
P5Q3 motherboard – P45 chipset
AMD:
- AMD Phenom II X4 955 Black Edition
processor – 3.2 GHz, 45nm, 125W - Asus M4A78T-E motherboard
– 790GX chipset, AM3 (onboard video disabled) - G.Skill
F2 memory – 2x2GB, DDR2-1000 @ 800MHz, 9-9-9-24
Measurement and Analysis Tools
- CPU-Z
to monitor CPU frequency and voltage. - CPUBurn
K7
processor stress software. - Prime95
processor stress software. - 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. - 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 regulate
the CPU fan speed.
Benchmark Test 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.
- TMPGEnc Xpress: Encoding a 1-minute long XVID AVI file to VC-1 (1280×720,
30fps, 20mbps).
Our testing procedure is designed to determine the overall system power consumption
at various states. To stress CPUs we
used Prime95 (large FFTs setting) or CPUBurn (which produced the higher power
draw). We also performed a short series of benchmarks featuring real-world timed
tests and synthetics.
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
TEST RESULTS
Both our Intel and AMD systems consist of a moderately priced motherboard with
DDR3 memory support, 2x2GB of DDR3 memory in dual channel set to the 1333 MHz
with timings of 9-9-9-24. A GeForce 9400GT graphics card, WD VelociRaptor and
OEM 400W 80 Plus Seasonic power supply round out the test configuration.
Test Results: General System Power Consumption | ||||
Test State | X4 955 BE | QX9650 | Q9550 | Q9550S |
Idle | 73W | 68W | 64W | 62W |
VC-1 Playback | 99W | 86W | 75W | 73W |
CPU Load (2 cores) | 157W | 122W | 120W | 105W |
CPU Load (4 cores) | 201W | 142W | 140W | 125W |
The Q9550S used slightly less power than the Q9550 during general power
consumption testing. System power was 2W less when idle and during VC-1 video
playback. Placing a load on the CPU increased its lead by 15W. It is undoubtedly
more energy efficient, but the difference is hardly what one would expect considering
the 65W rating. Our Core 2 Extreme QX9650 used only slightly more power than
the Q9550, which suggests its 130W TDP is quite conservative.
Benchmark Comparison | ||||
Test | X4 955 BE | QX9650 | Q9550 | Q9550S |
NOD32 | 2:27 | 2:23 | 2:31 | 2:31 |
WinRAR | 3:05 | 2:51 | 2:59 | 2:57 |
iTunes | 4:34 | 3:20 | 3:33 | 3:33 |
TMPGEnc | 2:52 | 3:07 | 3:14 | 3:15 |
PCMark2005 | 9004 | 9061 | 8760 | 8766 |
As expected, the Q9550 and Q9550S performed almost identically in our
benchmarks, with the subtle differences well within margins of error. Both chips
are only slightly behind AMD’s fastest, the Phenom
II X4 955 Black Edition.
Average Benchmark Power Consumption | ||||
Test | X4 955 BE | QX9650 | Q9550 | Q9550S |
NOD32 | 128W | 88W | 84W | 78W |
WinRAR | 128W | 98W | 96W | 87W |
iTunes | 137W | 92W | 89W | 81W |
TMPGEnc | 167W | 118W | 113W | 102W |
Est. Total Benchmark Power Consumption (Watt-hours) | ||||
NOD32 | 5.23 | 3.50 | 3.52 | 3.27 |
WinRAR | 6.58 | 4.66 | 4.77 | 4.28 |
iTunes | 10.43 | 5.11 | 5.27 | 4.79 |
TMPGEnc | 7.98 | 6.13 | 6.09 | 5.53 |
The Q9550S also used less power during the time it took to run each
timed benchmark, between 6W and 11W less depending on the test. The total difference
for all the benchmarks combined was 9%. If we operated the Q9550 system continuously
for a year running just TMPGEnc, it would draw 78.84 kWh more than the same
system with a Q9550S. According to the EIA
the average cost of electricity in the United States in March of 2009 was 11.38
cents per kilowatt-hour. Average savings for one year: $8.97. Average time to
recoup a $115 price difference: 12.8 years.
Undervolting
Perhaps the most important value factor is whether a Q9550 can meet or exceed the lower power consumption
of a Q9550S through undervolting. After some fiddling, we managed to
get our Q9550 sample stable at 1.024V according to CPU-Z (1.03125V setting in
the BIOS). The Q9550S was stable at a minimum of 1.064V (1.075V in the
BIOS), which coincidentally is the same voltage applied when idling with SpeedStep
enabled.
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Undervolted Test Results
Test Results: General System Power Consumption | ||||
Test State | Q9550 | Q9550S | ||
Stock | UV | Stock | UV | |
Idle | 64W | 64W | 62W | 63W |
VC-1 Playback | 75W | 75W | 73W | 74W |
CPU Load (2 cores) | 120W | 99W | 105W | 99W |
CPU Load (4 cores) | 140W | 117W | 125W | 118W |
Undervolted, our Q9550 produced a 21W improvement when 2 of its cores were
fully stressed and 23W when all 4 were put to to pace. These results place it
ahead by 6-8W of the Q9550S at stock voltage. Undervolting the Q9550S
resulted in only a 6-7W improvement. The difference between the two processors
when undervolted to their respective minimum stable voltage was negligible.
Average Benchmark Power Consumption | ||||
Test | Q9550 | Q9550S | ||
Stock | UV | Stock | UV | |
NOD32 | 84W | 75W | 78W | 74W |
WinRAR | 96W | 83W | 87W | 83W |
iTunes | 89W | 77W | 81W | 76W |
TMPGEnc | 113W | 95W | 102W | 95W |
Total Benchmark Power Consumption (Watt-hours) | ||||
NOD32 | 3.52 | 3.15 | 3.27 | 3.10 |
WinRAR | 4.77 | 4.13 | 4.28 | 4.08 |
iTunes | 5.27 | 4.56 | 4.79 | 4.50 |
TMPGEnc | 6.09 | 5.12 | 5.53 | 5.15 |
Undervolted, each processor used approximately the same amount of power
during our timed benchmarks.
FINAL THOUGHTS
While the Q9550S does indeed use less power than the Q9550, it is much
less than the 30W suggested by their TDP ratings. Thermal Design Power is an “up
to” specification indicating maximum power dissipation under the most extreme loads, so caution should be used when looking at these numbers.
We found that the difference in power consumption was much too small to justify
the $125 higher price-tag. To add insult to injury, our retail Q9550 sample could be undervolted
to the point where it became more energy efficient than the Q9550S at
stock voltage. Our Q9550S didn’t undervolt any better — when both
processors were set to their respective minimum operating voltages, the numbers
were indistinguishable. There were no significant performance differences between
the two.
The performance of our retail Q9550 sample suggests that Intel’s
45nm manufacturing process has matured. A Q9550 purchased today and
properly undervolted should come close to the energy efficiency of a
Q9550S. All that is required is a capable motherboard, a little
time, effort, and know-how.
For a user looking for energy efficiency both to reduce their system’s overall
operating cost and the amount of heat that needs to be dissipated, the Q9550S
may be a viable choice depending on the circumstances. If, for
instance, the system in question is mini-ITX, the Q9550S merits
some consideration: A SFF PC is difficult to cool and most mini-ITX
motherboards lack the ability to undervolt.
For corporations and OEMs which simply don’t have time to undervolt and stress
test each processor individually to ensure system stability, the Q9550S
is a questionable choice, given its current market price. The lifespan of the
processor is probably not long enough to offset the $100+ cost premium unless
the electricity rate is very high. The slower “S” models currently
cost about $75 more than their 95W counterparts — still high, but a far
more palatable price to absorb.
Our thanks to Intel
for Q9550S sample.
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Articles of Related Interest
AMD Phenom
II X2 550 BE & Athlon II X2 250
AMD Phenom II X4 955 Black Edition for
AM3
Phenom II: AMD pulls closer
Intel Core i7: Nehalem Launched
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