Intel's DH55TC and Core i5-661 - Clarkdale

Jan 04 2010


intel core i5

Intel DH55TC & Core i5-661 (Clarkdale) Review

The family of processors code-named "Clarkdale" has sparked a great deal of interest since its existence and some basic performance information spread out across the web in late September.  Teasing home theater PC (HTPC) enthusiasts with incredibly low power usage and built in HD codec bit streaming all packaged together with enough performance to tempt those in need of a full featured HTPC. 

Given Intel’s somewhat troubled history with integrated graphics there has been a lot of skepticism on how well (and if) Intel can deliver a serious contender for space in your A/V stack.


Clarkdale Platform

Before digging into our review sample let’s take a quick look at the Clarkdale lineup and supporting platform.

Like all LGA 1156 CPUs Clarkdale integrates the functions previously handled by a chipset's north bridge into the CPU.  While similar to earlier Core i5 chips in this way, Clarkdale also has some significant differences.  The biggest is that the GPU has also been integrated onto the CPU package, in addition all Clarkdale CPUs are manufactured using a 32nm process technology (the GPU is 45nm) and are dual core processors.  

The Clarkdale family is comprised of three discrete lines of CPUs; Core i5, Core i3 and Pentium G6XXX.  Each line has a slightly different set of features; to make the feature discussion easier please refer to the cheat sheet below.

Intel Clarkdale Cheat sheet

As we can see every chip in the family except the i5-6X1 (e.g. i5-661, our review sample) carries a 73W TDP.  At first look this seems a bit high for a CPU aimed at the HTPC enthusiast, but it’s critical to remember that this is the TDP for both the CPU and GPU, which is actually quite good.  Taking a closer look it becomes clear why the i5-6X1 carries an 87W TDP, as the GPU runs at 900MHz instead of 733MHz like the rest.   The extra MHz won’t help for any of our use cases making it of more interest to the casual gamer.

The only notable feature missing from the i3 versus the i5 is Turbo Boost.  Turbo Boost is an interesting feature where a single core temporarily runs at a faster speed, so for example a single core on the 3.33GHz i5-661 can run at 3.6GHz; a nice boost for single threaded applications.

Both the i5 and i3 support Hyper-Threading (HT); don’t worry Pentium 4 owners this time it’s a good thing (21% gain in Handbrake transcoding).  Both also support full dual-stream hardware accelerated (HWA) video decoding (i.e. Blu-ray picture-in-picture) for MPEG2, VC-1 , and AVC/H.264 as well as HD codec bit streaming (yes, you read that right; bit stream TrueHD and DTS-MA – huzzah!).  Rounding out the notable specs is VT-x, which while not a huge feature is a nice to have if the HTPC also serves time as a PC and you want to use XP Mode in Windows 7.

Where the i5 and i3 are quite similar the G6XXX gets stripped down; losing HT, dual stream video HWA, and one of the more compelling features to HTPC enthusiasts - HD codec bit streaming.   That said, it should still be a competent performer, very similar in practice to results achieved with a G45 based HTPC (although if that’s what you want an E5300 + DG45ID is a better deal).  Personally, if budget was an issue I’d probably try to cut the $26 difference to the base i3 out somewhere else.

Technically there are four chipsets that will support the Clarkdale family; H55, H57, Q57 and P55.  The P55 has been out since September and makes up the “technically” because while a Clarkdale CPU will run in it, the GPU won’t; so for the purpose of this review it will be ignored.

The H55, H57 and Q57 chipsets are almost identical in feature set; most of the differentiators are aimed at the corporate market.  The only relevant differences between the three are the number of USB ports (H55 can have twelve and H57/Q57, fourteen) supported and that boards based on H57/Q57 can optionally support RAID. 

Intel will have five boards available; three micro-ATX, one ATX and one mini-ITX.  See the break-out below for the details.

Clarkdale Peak Boards

The lineup is pretty thorough, but only the DH55TC (our review sample) will have global availability immediately and should come in at around $100.  There will also be boards from other motherboard manufacturers available immediately as well.

Enough background, let’s dig into the good stuff.

Hardware and Specifications

The DH55TC is a pretty minimalist micro-ATX board with a well thought out layout except for two minor exceptions. 

Intel Core i5

The first, and most annoying, is that the clip to hold the fan wire on the stock heat sink and fan (HSF) will make contact with RAM in the first DIMM slot (or block it if the RAM has a heat spreader) when installed in the preferred orientation.  While it’s not a huge problem to rotate the HSF, the fan wire has to be released from the clip and isn’t flush against the HSF.  The second issue is the placement of a capacitor right next to the four pin ATX power, which will cause problems if the power supply (PSU) has an eight pin connector. 

intel core i5 clarkdale

The I/O panel has all the necessary ports including a PS2, DVI-D, VGA, HDMI and plenty of USB.  Notably missing for HTPC versatility is a S/PDIF connector, but there is a header present to BYOS[/PDIF] if it’s an essential feature.

The BIOS is straightforward (full gallery below) with just a couple areas to discuss. 

intel core i5 bios

Like most boards, the DH55TC’s default SATA controller mode is IDE and must be changed to AHCI before OS installation to make full use of NCQ or eSATA features.  Neither Vista nor Windows 7 required extra drivers (i.e. F6 + floppy) during the install so in my opinion it would be better for the board to ship in the optimal configuration.

intel core i5 bios

One really nice feature that I’ve never seen before is the ability to choose how the power LED should behave in S3 mode.   Options include “Off”, “Blink”, “On”, and “Alternate Color” (only some cases will support this mode).   In the first case to house this board a strange issue was encountered where selecting “Off” would turn off the LED initially when the system entered S3, but after a few hours it would come back on.  The issue wasn’t reproducible on another case so it was most likely the age and/or cheapness ($15); somewhat annoying but a workaround was available by selecting “Alternate Color” which [oddly] produced the desired result.

See below for the full gallery of all the BIOS pages as previously mentioned.

 Bios Pic Bios Pic Bios Pic
Bios Pic Bios Pic Bios Pic
Bios Pic Bios Pic Bios Pic
Bios Pic Bios Pic Bios Pic
Bios Pic Bios Pic Bios Pic
Bios Pic Bios Pic  

System Configuration


  • DH55TC micro-ATX
  • Core i5-661 (3.33Ghz 87W TDP)
  • A-DATA 4GB (2 x 2GB) DDR3-1333
  • Seagate 200GB 7200RPM Hard Drive
  • Antec Earthwatts 380W PSU

Both Vista and Window 7 were tested, and in all the major areas (Media Center, SageTV, and Blu-ray playback) the experience was identical.  The majority of testing was performed with Windows 7 however, so there may be some discrepancies as we discuss specialized features in detail.

OS installation was very easy, but unfortunately neither Vista nor Windows 7 included drivers for the integrated network interface which is not a problem if prepared -- just keep that driver CD handy.  Overall the system is fast and incredibly stable.  Despite my best efforts (only the HSF and PSU fans were used in all of the tests) I was unable to make the system crash or lock-up.  Hibernation (S4), standby (S3) and resume work brilliantly; no issues going into or coming out of the different power states were experienced.   For completeness, tuners from AverMedia (Duet/M780) and Hauppauge (HVR-2250/HD-PVR) were tested for stability and functionality with Media Center (Windows 7 and Vista) and SageTV (Windows7* and Vista) without issue.

*Windows 7 is not currently supported by SageTV, all tuners were tested on 7 and everything worked as expected except for the HVR-2250 which exhibited the same dual-tuner issue experienced on my reference 780G based HTPC.

Also notable is that the video configuration interface was completely redone for Clarkdale, exposing more settings and making the UI much easier to use than the previous version.  For those who need to create custom resolutions, the process is both straight forward and full of options to get exactly what you need.

Intel Core i5 Timing Options

All of the testing was done on a 1080p plasma so there wasn’t an opportunity to really dig into the custom resolution feature (the display was correctly detected and configured when connected).

Intel Core i5

But I did play with the overscan correction feature a bit.  To get a feel for how well it works 1-1 pixel mapping was disabled on the TV, inducing some overscan.  Conveniently the setting is exposed through a set of sliders on the main page (anyone familiar with the Nvidia and ATI interfaces should find it very similar), and works exactly as it should.

Kind words for the TV Wizard still escape me however; allowing it to run resulted in 800x600 being selected as the optimal resolution.  Apparently this application is intended to be used to configure CRT displays so perhaps the behavior is forgivable, but if that is the case I wish that it wouldn’t pop up for digital displays as those most likely to click through the wizard are also the least likely to realize that the settings it chooses aren’t correct.


One of the most interesting features packed into the Core i3/i5 is HD codec bit streaming so it’s no longer necessary to buy an expensive sound card (Xonar/X-Fi) or a discrete video card intended for gaming (ATI 5XXX) to add Dolby TrueHD and DTS-MA pass-through to the AVR.  Particularly interesting is how Intel’s approach with this feature is exactly the opposite of ATI’s with the 780G/785G IGP which only offers stereo (vs. multichannel) LPCM over the HDMI connection. 

Looking at the “Sounds” control panel for the HDMI audio device on Vista and Windows 7 it’s clear that support is presented at the OS level.

Clarkdale Supported Formats Vista Clarkdale Windows 7 Audio

I still believe that “lossless audio is lossless audio”, but this is an important step forward because HTPCs are all about choice and flexibility (it’s also nice to take away a talking point from the standalone BD player guys :)); to bit stream or not can now be a personal preference and not a hardware limitation.  What’s particularly brilliant about the implementation is that it just works with every mainstream Blu-ray player so retail versions of PowerDVD, Total Media Theater or WinDVD can be selected based on preference and not by what is required with a particular sound card (Arcsoft for the ASUS Xonar, Cyberlink for Auzentech’s X-Fi).  And if you install ffdshow 3164+ (at least on Window 7, Vista was not tested) HD audio bit streaming also works in DirectShow based players including Media Center and SageTV.

Video - Good

Starting with Blu-ray playback, simply put the results were excellent.  Cyberlink PowerDVD (PDVD), ArcSoft Total Media Theater (TMT) and Corel WinDVD (WinDVD) were all tested and each player performed very well.  The current retail version of PDVD Ultra and WinDVD support Clarkdale and Arrandale (mobile Clarkdale), where the update to TMT3 will be available in early February.

PDVD and TMT did require some additional configuration to enable HD bit streaming (selecting the correct output from the audio tab of the respective settings dialog), where WinDVD enabled the feature automatically.  The experience from Media Center was most seamless using PDVD, as its “integrated” player is both remote friendly (WinDVD is not) and it was possible to enable HD codec bit streaming (I couldn’t figure out how to do this in the TMT integrated player).

AVC/H.264 (Quantum of Solace) Blu-ray playback registered between zero and four percent CPU utilization and VC-1 (The Dark Knight) came in at a slightly higher two to five percent, confirming that HWA is working quite well on the platform. 

The results were very similar with 1080p AVC/H.264 and VC-1 content in M2TS and MKV. 

Clarkdale Hardware Results

One of the challenges with VC-1 content stored in MKV is how the content is presented by the splitter (instead of using the VC-1 media type, WVC1 is used).  Some early reviews have incorrectly noted issues with VC-1 HWA because of this, incorrectly finding problems with the platform where the root cause is simply a media type incompatibility leading the WMV DMO (Microsoft’s software based WMV decoder) or another software based decoder (like ffdshow) to be used in the playback graph.  On ATI platforms the solution is to grab the MPC-HC video decoder.  While there are indications in the source code that the MPC-HC developers are working on VC-1 acceleration for Intel graphics, it’s not working yet.  Fortunately there is a solution in Intel’s Media SDK.

There is a lot of good stuff in the Media SDK for developers looking to get a head start using the platform (both CPU and GPU), but most importantly the fact that it exists is a strong signal that Intel is serious about media consumption on their hardware.  The most interesting part (for the purpose of this review) is the sample WMV decoder, which after some customization works quite well with WVC1 content contained in MKV.  With this customized filter, we see CPU utilization that is very much in line with what we expect from proper HWA.  For those interested in using the customized decoder (tested on Vista and Window 7) it can be downloaded here; a little MissingRemote value add :).

Integrated graphics (IGP) have historically struggled with proper deinterlacing support, so we are going to dig into the i5-661’s capabilities in this area.  To probe the capabilities of the different graphics solutions tested, patterns found on the Spears & Munsil HD Benchmark disc were selected.  There are several patterns on the disc so just the most common types will be discussed. 

We will be looking at the source adaptive 2-2 (two fields per frame, equivalent to 30fps)and 2-3-2-3 (PF-T) (two fields for the first frame then three fields containing one frame and one field of the next image, most commonly used for transferring 24p film to 60i video) wedge and the edge adaptive “Jaggies” (tests the ability to deinterlace without jagged stairstep patterns on edges) tests below. 

In the source adaptive tests moiré should be present only in the last quarter of the wedge, overall brightness should be consistent, and there should not be any flickering.  In the “Jaggies” test a rectangular bar rotates through a large inner circle of alternating black and white lines, as it moves the edge of the bar should remain smooth (not jagged) along the length of the bar, any distortion that occurs as it passes through the alternating lines should remain close to the bar and the alternating lines in the circle must be solid and not flicker.

Intel Core i5-661 (

  • 2-2: moiré was present up to ½ of the wedge, pattern was consistent and solid
  • 2-3-2-3 (PF-T): moiré was present up to ½ of the wedge, pattern was consistent and solid
  • Jaggies: The moving bar is very straight.  The circle maintains alternating pattern, and only a thin line of distortion is present as the bar moves through it.

Intel GMA X4500HD (

  • 2-2: moiré was present slightly past ¼ of the wedge, pattern was consistent and solid
  • 2-3-2-3 (PF-T): moiré was present slightly past ¼ of the wedge, pattern was consistent and solid
  • Jaggies:  The circle maintains alternating pattern, but the moving bar is very jagged.

ATI 4650 (Catalyst 9.12)

  • 2-2: moiré was present on slightly more than ½ of the wedge, pattern was consistent and solid
  • 2-3-2-3 (PF-T): moiré was present on slightly more than ½ of the wedge, pattern was consistent and solid
  • Jaggies: The moving bar is quite jagged as it moves.  The circle is drawn correctly, but a long tail of distortion trails the bar as it moves.

ATI 5770 (Catalyst 9.11*)

  • 2-2: moiré was present up to ½ of the wedge, pattern was consistent and solid
  • 2-3-2-3 (PF-T): moiré was present up to ½ of the wedge, pattern was consistent and solid
  • Jaggies: The moving bar exhibits a little jaggedness, but is mostly smooth.  The circle is drawn correctly, but a long tail of distortion trails the bar as it moves.

Nvidia 8600GT (Nforce 195.62)

  • 2-2: moiré was present on slightly more than ½ of the wedge, pattern was consistent and solid
  • 2-3-2-3 (PF-T): moiré was present on slightly more than ½ of the wedge, pattern was consistent and solid
  • Jaggies: The moving bar is very jagged as it moves.  The circle is drawn correctly, but a very long tail of distortion trails the bar as it moves.

Based on the results across all of the tests it’s obvious that Clarkdale is a solid performer; owning the edge adaptive and performing as well as or better than the discrete cards in the source adaptive; unless the HTPC will also be used for serious gaming there’s not much need for a discrete card.  That said, what’s clearest from the source adaptive tests is that there is a lot of room for improvement from all the vendors (although the GMA X4500HD's performance bodes well for Clarkdale); and I hope each one of them will make improvements in this area.

*The borrowed ATI 5770 had to be returned before 9.12 was available

So that was the good, now it’s time for the “needs improvement”. 

Video - Needs Improvement

Most of the testing was conducted through a Denon AVR-1909, and when connected to this audio video receiver (AVR) the board was unable to create a secure HDCP path to the display.  The issue is easy to workaround if AnyDVD HD is present, but obviously it should just work. 

intel core i5 hdcp error

This issue does seem to be limited to the AVR-1909 as other AVR (including a Denon AVR-3808) tested did not exhibit the problem.

UPDATE - 03/22/2010:

I picked up a 15' HDMI cable per Intel's recommendation and using it the board was able to successfully negotiate a HDCP connection during Blu-ray playback.  A big thanks to Intel for the follow up and workaround.

Two other issues with the shipping driver ( were also uncovered in testing.  First when video is played using default settings the content is too dark (i.e. the brightness setting needs to be changed from 45 to 77 on my TV) and the second is an issue where values 16-21 are clipped and indistinguishable.  Intel is aware of the problem and provided a beta version of the video driver which mostly fixes the issue, hopefully with some more time in the oven everything will be perfect.

The operative phrase with this issue is “by default”, and that shouldn’t be taken lightly.  One of the strengths of the GMA X4500HD was that it just works out of the box to deliver excellent picture quality.   Thankfully addressing the issue is quite easy; just open up the graphics properties, select the “Media” tab, check “Override Application Settings” and fire up your favorite pludge pattern then adjust the “Brightness” value.

Clarkdale Correcting Black Clipping

Fine tuning can be a bit difficult using only the mouse, so click-and-hold the slider and use the right/left arrow keys to get the perfect black.  Once this adjustment is made, both the brightness and clipping issues disappear and the full PC and video colorspace (0-255 for non-video content and 16-235 for video) is represented properly and we’re back to the excellent picture quality expected from the platform. 

Performance and Power Usage

To get a good feel for performance, instead of looking at a bunch of synthetic numbers we're going to dig into two of the most demanding scenarios that justify the need for some BHP in the HTPC.  Please note that in all of the graphs lower is better.

In the first test we’re going to look at ShowAnalyzer’s  (SA) performance with various content types.  For those unfamilar with SA it is an application that scans video files for commercials so other applications can remove or skip them during playback.  SA is one of the most demanding applications I’ve seen, and makes an excellent test tool because of the stress it places on the box both through large amounts of I/O and excellent multithreaded CPU punishment.

In this test three containers (MPG, WTV and TS) with MPEG-2 and H.264 were scanned on four different machines.  All of the machines were configured with 4GB of RAM and a 3.5” 7200RPM SATA drive running in AHCI mode.

intel core i5 performance

Looking at the results, what is most surprising is how competitive the i5-661 is with the quad core parts.  In every test it was faster than the 9950, and while slightly slower (within a few seconds) than the Q6600 with MPEG2 files it took almost five minutes less when scanning H.264 content.  The E5200 was included to provide a reference for what a low power HPTC brings to the table.

The next performance test was a series of transcoding runs using Cyberlink MediaShow Espresso and Handbrake 0.94.  Espresso is an interesting application because it supports CUDA and Stream (GPU assisted decode/encode technologies from Nvidia and ATI) as well as GPU assisted decode on Clarkdale.

intel core i5 test results

Two approximately 30 minute recordings were selected to transcode using the built in iPhone profile.  The i5-661 was paired against a Q6600 to judge a pure software transcode, and an E5200 using an ATI 4650 (Stream) and an Nvidia 8600GT (CUDA).  With the exception of MPEG2 content on the 8600GT in each case the i5-661 was significantly faster.  It would be easy to discount these results with claims about the CPUs/GPUs used to compare, but the point is not just to discuss raw performance but performance inside a specific power envelop.  Even the E5200 when paired with a discrete card drew slightly more power than the i5-661 under load.

In our last test Handbrake was used because it’s free, incredibly popular, and a great way to test multithreaded CPU performance.  Because it does not utilize (as far as I know) any GPU assist the discrete card was removed from the E5200 based system and measured against the same group as the first test.

intel core i5 handbrake performance

As we can see the i5-661 is very close in performance to the two quad-core systems, but significantly more power efficient under load.  Only the E5200 beats it, but taking more than twice the time to complete the test.

Rounding out our look at power consumption the table below was prepared.

intel core i5 power usage

It is important to note that all of the numbers above were measured with the 87W i5-661 so the numbers should be somewhat lower using a 73W part, which makes more sense in an HTPC.  Even with the 87W CPU I had no problem running the system with only the fans on the HSF and PSU keeping everything cool.


Intel has done what many would not have thought possible by creating an incredibly compelling platform for the HTPC.  While not perfect, and sporting some teething issues, it’s hard to argue with the features and value that the platform offers.  Of course while my id would like the entry price to be a bit lower (the cheapest part that supports HD audio is $113) my ego has a hard time reconciling that desire with the feature set provided.

The Clarkdale solution will now up the bar yet again for other manufacturers seeking to compete on a feature level, and poses an interesting question to the likes of soundcard manufacturers struggling for relevance after betting on being the sole bit stream providers—why spend an extra $150-250 on their solution when it is included “for free”. Of course if you already have a perfectly good system and graphics solution, the idea of replacing your motherboard/CPU might make you cringe, and as stated this platform is not ideal for hard-core gamers.

For the HTPC crowd however, Clarkdale brings us that much closer to HT Nirvana. It’s a (somewhat) affordable solution which gives the user low power draw so it can run cool and quietly, supports the same HD bit stream capabilities of the highest end audio cards; while arguably providing the standard in HTPC picture quality…and it even properly handles standby and hibernation!


  • Excellent picture quality for every format tested
  • Deinterlacing performance as good as or better than discrete cards
  • HD codec bit streaming
  • Low power consumption
  • Performance competitive with previous generation quad cores
  • Correct[able] black levels for all content – pictures and video with minimal tweaking (should work flawlessly in future driver versions)


  • HDCP issues with Denon AVR-1909
  • Some tweaking required to get proper black and brightness levels during video playback with current driver version
  • G6XXX line has drastically reduced features that could cause confusion

Lastly, I would like to thank Intel for providing the review sample.

Website design by Yammm Software
Powered by Drupal