Intel Core 2 Quad Q8400 CPU Review

Intel Core 2 Quad Q8400 CPU Review

The Core 2 Quad Q8400 is a 2.66GHz quad-core processor from Intel, built on the new 45nm process with a 1333MHz FSB and 95W TDP. While it might not be the latest Core i7 model, it is a good option if you are looking to just upgrade your processor in an older rig that supports it. Today we take a look at the Intel Q8400 and see what sort of performance increase it brings to a first generation Core 2 Duo desktop previously using a 1.86GHz E6300. Read on to see what we found.


Our test system had the following specifications:

  • Operating system: Windows Vista Business SP2
  • Processor 1: Intel Core 2 Duo E6300 @ 1.86Ghz
  • Processor 2: Intel Core 2 Quad Q8400 @ 2.66GHz
  • Motherboard: ASUS P5B Deluxe Wifi-AP with Intel P965 Express
  • Memory: 3GB DDR2 SDRAM (1GB x 2, 512MB x 2)
  • Hard drive: 80GB Hitachi @ 7200RPM
  • Video card: Gigabyte 7600GT with 256MB GDDR3
  • Power supply: SeaSonic 330W

The desktop that we chose for this review is a very early Core 2 Duo machine, purchased around the initial launch of the platform back in the summer of 2006. Obviously this desktop can’t support the latest Core i7 processor without replacing the motherboard and RAM, but it can support the Q8400 and retain all of its old hardware. By replacing just the processor we can see exactly what gains can be had in a system that is now pushing 3 years in age…ancient in the computer industry.

Clocked at 2.66GHz, the Intel Core 2 Quad is part of the Yorkfield 45nm series. This processor class features 2MB of L2 cache per side, totaling 4MB. It offers a 1333MHz FSB and 95W thermal envelope. Compare this to the older E6300, which was clocked at 1.86GHz with 2MB of L2 Cache total. It had a 1066MHz front side bus and a lower 65W TDP. Although the E6300 technically has a 30W lower TDP, in some of our tests we actually found the Q8400 to draw less power under different circumstances. This is a side-effect of the newer and smaller manufacturing process.


The desktop used for this review isn’t the latest and greatest by any stretch of the imagination. It is pushing almost three years since it was originally built, which makes everything even more impressive when it can be compared to some of the desktops released in the past year. The main weakness that this machine still has though is its slow NVIDIA GeForce 7600GT graphics card, which even the fastest processor on the planet can’t help.

The first benchmark we ran to get an overall view of system performance before and after the upgrade was PCMark05 and PCMark Vantage. Both benchmarks saw a 50-60% increase moving from the E6300 to the Q8400.

CPUPCMark05PCMark VantageIntel Core 2 Quad Q8400 @ 2.66 GHz8044 PCMarks4625 PCMarksIntel Core 2 Duo E6300 @ 1.86 GHz5168 PCMarks3082 PCMarks

Next up is 3DMark06, which as mentioned before, saw little gain to the 3D performance after the processor upgrade. To see this increase we would need to upgrade to a graphics card that isn’t three years old.

When we breakdown the CPU components of PCMark05 and 3DMark06, the Q8400 gives some pretty strong results. Compared to other processors we have reviewed, it falls just above the Phenom x4 9850 BE overclocked to 2.9GHz.

CPU3DMark06Intel Core 2 Quad Q8400 @ 2.66GHz3404 3DMarksIntel Core 2 Duo E6300 @ 1.86GHz3159 3DMarks

PCMark05 and 3DMark06 CPU test performance comparison results(higher scores mean better performance)

CPUPCMark05 CPU Test

3DMark06 CPU TestPhenom II x4 955 @ 3.2 GHz9693 PCMarks4242 3DMarksPhenom II x4 940 @ 3.0 GHz9020 PCMarks4241 3DMarksCore 2 Quad Q8400 @ 2.66 GHz8459 PCMarks3888 3DMarksPhenom II x4 810 @ 2.6 GHz7750 PCMarks3684 3DMarksPhenom x4 9950 BE @ 2.6 GHz7682 PCMarks3551 3DMarksCore 2 Duo E6300 @ 1.86 GHz4705 PCMarks1612 3DMarks

Looking at wPrime when comparing the E6300 to the Q8400, we see a huge decrease in test duration. The quad-core processor gives results that are 3 times faster than the original processor.

wPrime benchmark comparison results(lower numbers mean better performance)

CPUwPrime 32 timeCore i7 920 @ 2.66 GHz9.1sPhenom II x4 955 @ 3.2 GHz11.859sPhenom II x4 940 @ 3.0 GHz

12.361sCore 2 Extreme QX6850 @ 3GHz13.869sPhenom II x4 810 @ 2.6 GHz14.397sCore 2 Quad Q8400 @ 2.66 GHz14.133sCore 2 Quad Q9450 @ 2.66 GHz14.625sCore 2 Duo E6300 @ 1.86 GHz43.574s

The final test we ran on the newer processor only, to compare it to some of the faster AMD Phenom processors is our Audio Compression test. The Intel Q8400 compressed the 14 WAV files in 32 seconds, which pairs up close with the Phenom II x4 955.

Audio Compression Test (lower scores mean better performance)

CPUAudio Test (HH:MM:SS)

Phenom II x4 955 @ 3.79 GHz (OC)00:00:32

Phenom II x4 955 @ 3.2 GHz

00:00:35Phenom II x4 940 @ 3.0 GHz00:00:35Core 2 Quad Q8400 @ 2.66 GHz00:00:36Phenom II x4 810 @ 2.6 GHz00:00:41Phenom II x3 720 BE @ 2.8 GHz00:01:22

Besides benchmarks the faster processor helped out in some of the daily tasks seen in my HTPC. Very high bitrate 1080P videos used to have problems with audio sync with the old processor, where midway through a movie the video would be running .5 to 1 second behind the audio. After switching to the faster processor the problems were eliminated. Upgrading to a graphics card that fully supports GPU-assisted MPEG4 decoding would have also probably helped.

Save your old machine

As we mentioned above, the system we used was a stock three- year old desktop into which we just dropped this processor. Just because you have an old rig doesn’t mean it can’t be upgraded to modern levels of performance. The processor was the only change in this desktop, with the old (and slow) DDR2-667 RAM, Intel 965P chipset motherboard, and 80GB hard drive still being used and fully compatible. In some systems sold with the Intel P4 processor that have compatible motherboards, this type of upgrade would yield even greater performance boosts. If you took this time to upgrade the graphics card, you could easily have a desktop that would blow most retail machines away for a fraction of the cost.

Just make sure you check the rating of your power supply before you start throwing faster and more power consuming components into an old desktop. If you didn’t over-spec the power supply originally it might be pushed to its limit under stress. Also, be certain that your motherboard would support a processor upgrade. Sometimes, just because the socket on the board matches the processor doesn’t mean it’s compatible, since the CPU must be recognized by the BIOS as well.

Power Consumption

One of the first things I checked after upgrading the processor was how much of an impact the quad-core processor was going to have on my power bill. One might guess that more cores and higher clock speed might equal higher power consumption, but that was only partially true. Under a light load and close to idle activity, which you might see while browsing the web, the original E6300 used 94 watts of power. Under a heavy load of wPrime, power usage jumped to 116 watts. With the Q8400 idle power consumption was 89 watts at idle, 5 lower than the old dual-core. Under a peak load it jumped to 137 watts, much higher, but under normal daily use most people don’t have their processors pegged. For a HTPC which is going to be on and downloading stuff in the background overnight, you will probably end up saving power with the much faster processor.







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