Introduction

The Intel NUC category has been an interesting product line to analyze, as it provides us with insights into where the traditional casual / home use desktop market might end up. Officially falling under Ultra-Compact Form Factor PCs (UCFF), units in this category take miniaturization to the extreme by even making 2.5" drives unnecessary. Last year, we reviewed Intel's first NUC. Fast forward to the present, and we have the Haswell-based NUC already in the market. How does Haswell improve upon the original NUC? Before going into that, a little bit of history is in order.

The ultra-compact form factor (UCFF) for PCs was originally championed by VIA Technologies with their nano-ITX (12cm x 12cm) and pico-ITX (10cm x 7.2cm) boards. Zotac was one of the first to design a custom UCFF motherboard (sized between nano-ITX and pico-ITX) for the ZBOX nano XS AD11 based on AMD Brazos. The motherboard was approximately 10cm x 10cm. Intel made this motherboard size a 'standard' with the introduction of the Intel NUC boards in May 2012. The first generation Intel NUCs were both launched with Core i3 17W TDP CPUs. While one model had a GbE port, the other traded it for a Thunderbolt port.

The Haswell NUCs come in two varieties too, but Intel has opted for a more conventional configuration this time around (particularly due to the slow uptake in Thunderbolt adoption in the target market). The following table provides a quick look at the specification of the two Haswell NUCs, with our review configuration highlighted. The WYB suffix refers to the board alone, while the WYK suffix refers to the kit with the chassis. The WYKH increases the dimensions of the chassis to support a 2.5" HDD / SSD in addition to the mSATA drive.

The layout of the board is specified in the diagram below. The integration of the PCH into the processor is one of the advantages of the Haswell NUC compared to the Ivy Bridge NUCs (which used a QS77-Express chipset).

For such a small motherboard, the unit does pack quite a punch. The choice of the WLAN card as well as the mSATA disk is left to the system builder. This is in contrast to the Gigabyte BRIX, where consumers are advised not to remove the supplied WLAN card. The extra degree of freedom will definitely be appreciated in some circles. The default chassis provided by Intel employs active cooling and has a height of only 1.4 inches. This rules out the possibility of cramming in a 2.5" drive into the enclosure of the WYK, even though the motherboard provides SATA ports. The WYKH models alter the chassis dimensions to take advantage of the on-board port.

In the remainder of the review, we will look into our choice of components for completing the NUC build, some notes on the motherboard design, performance metrics / benchmarks, HTPC aspects and round up the review with some coverage of miscellaneous aspects such as power consumption and thermal performance.

Hardware and Setup Impressions

The Intel D54250WYK, unlike other off-the-shelf PCs, needs some components in order to complete the build. It is a barebones machine, in the sense that the power cord, RAM, storage as well as WLAN card need to be supplied in addition to the operating system. For the cost price, the user gets the motherboard (including CPU) and chassis, as well as a 65W (19V / 3.43A DC) adapter. The unit, however, has wired pigtail connections to the chassis sides for acting as the antennae for a WLAN card. The power cord needed is a C6 type that plugs into the power adapter's C5 type connector. The 3-plug C6 connector is also known as a cloverleaf connector. It does keep costs for Intel down, but it would have been really nice to localize this component to the country of sale. The kit also comes with a VESA mounting bracket.

Building the NUC is incredibly simple. There are four screws that hold the chassis together and removing them gives access to the motherboard. From here the end user can install up to two 8GB DDR3 SO-DIMMs. The bottom mini-PCIe slot accepts a half height card (perfect for WiFi) while the top slot can take a full height card or an mSATA drive. The antenna pigtails for WiFi are already routed to the appropriate spot inside the chassis.

Intel sent along its mSATA SSD 530 (180GB), which is a SandForce based mSATA drive using 20nm MLC IMFT NAND. SandForce controllers work very well in mSATA form factors since they don't require any external DRAM. For the RAM, we have 2x 4GB CT51264BF160B SODIMMs from Crucial. Handling the WLAN side of the equation is the 7260HMW, Intel's dual band 2T 2R 802.11ac mini-PCIe card solution.

The soldered down CPU (Intel Core i5-4250U with the HD5000 IGP) and the fan / cooling system are on the other side of the motherboard, and not visible in the pictures above. On the same side, we have a HTPC header (with HDMI CEC) on the side of the CMOS battery (referred to as the 'custom solutions header' in Intel's technical documentation for the product). In addition to the mSATA port, we have a SATA port and a SATA power connector as well as a dual-port internal USB 2.0 header. The Nuvoton NCT5577D embedded controller acts as a hardware monitoring subsystem. The motherboard also has a CIR sensor in the front panel.

A view of the assembled system is also provided in the gallery above. One of the points to note is the presence of the thermal pad on the bottom cover right below the SSD / WLAN stack. In the first revision of the NUC, Intel faced some heat for messing up the thermals. In particular, high temperatures causes the SSD to stop working. These temperatures were the result of either high disk activity or heavy WLAN traffic. A thermal pad solution was provided for the original NUC after release of the product. With the Haswell NUC, the thermal pad solution comes pre-integrated. The fan speeds also seem to be a bit on the higher side throughout usage. Consumers used to fanless PCs are definitely going to be a bit upset with the constant hum from the unit, but we do have passive cooling solutions from third-party vendors (at the cost of system size).

The choice of components in our build have an approximate cost breakdown for the hardware as below. It is possible to hit lower price points with judicious choice of DRAM and SSD capacity.

On the software side of things, Windows 8 Professional x64 was installed without any hiccups. All necessary drivers were available on Intel's website. In addition to the host of benchmarking programs, we installed the Netflix Windows 8 app for evaluating streaming aspects. For the HTPC-related section, we installed MPC-HC v1.7.1 and madVR v0.86.11. Many users prefer XBMC as a one-stop interface for all HTPC activities. Some benchmarks were also run using XBMC v12.3.

Performance Metrics

The NUC was evaluated using our standard test suite for low power desktops / industrial PCs. Note that some of the benchmarks are pretty recent (such as x264 v5.0 and 3D Mark 2013). Loaner samples haven't been tested with these new benchmarks. Therefore, the list of PCs in each graph are not the same.

Windows Experience Index:

Our NUC build clocks in at 5.3 in Windows 8's experience index. The weak point here is the HD5000 graphics, as expected.

Users looking for more graphics power within a similar form factor would do well to look at Gigabyte's BRIX Pro which comes with Intel's Iris Pro graphics.

Futuremark Benchmarks:

Miscellaneous Benchmarks:

These are impressive benchmark numbers when the size of the system is taken into consideration.

Networking Performance and Streaming Aspects

In this section, we will take a look at the networking capabilities of the unit and also our standard HTPC streaming tests (involving YouTube and Netflix). Starting with this review, we are standardizing our evaluation of the wireless networking capabilities of UCFF and industrial PCs. Our standard test router is the Netgear R7000 Nighthawk configured with both 2.4 GHz and 5 GHz networks. The router is placed approximately 20 ft. away, separated by a drywall (as in typical US buildings). A wired client (Zotac ID89-Plus) is connected to the R7000 and serves as one endpoint for jPerf evaluation. The UCFF PC is made to connect to the two wireless SSIDs and jPerf tests are conducted for both TCP and UDP transfers with pre-set transfer parameters.

In our NUC build, Intel's Dual-Band Wireless-7260 delivers 2T2R 802.11ac speeds and provides very good throughput numbers when used with an appropriate router. As the gallery below shows, the 2.4 GHz band is able to deliver TCP throughput in the region of 86 Mbps and UDP throughput in the region of 96 Mbps.

The theoretical bandwidth number for 2x2 802.11ac is 867 Mbps. Practically, in the 5 GHz band, the 7260's TCP throughput is around 210 Mbps and UDP throughput is around 239 Mbps in our test setup.

Network Streaming Performance - Netflix and YouTube

YouTube and Netflix are two very popular streaming services utilized on HTPCs. With Windows 8, Silverlight is no longer necessary for Netflix streaming. The Netflix app on Windows 8 supports high definition streams (up to 5.8 Mbps) as well as 5.1-channel Dolby Digital Plus audio on selected titles.

It is not immediately evident whether GPU acceleration is available or not from the OSD messages. However, GPU-Z reported an average GPU utilization of 4% throughout the time that the Netflix app was playing back video. The average power consumption was around 8.5 W. Coming it at less than 10 W for the whole system while streaming HD video is very impressive. The spikes in the GPU usage were observed whenever the subtitles or control OSD kicked in. There is obviously some correlation between these spikes and the recorder power consumption at the wall.

One of the issues that I faced with the Netflix app was that bitstreaming HD audio (Dolby Digital Plus) would just not work. The playback was jerky to the point of being unwatchable and with either no or intermittent audio output to the AV receiver. Apparently, this is an issue faced by multiple users, and the problem stems from the Intel Display Audio Driver. Intel's rep on the forums, however, has been unable to reproduce the issue. So, it looks like many users are being left high and dry, unable to take advantage of one of the most important aspects of running Netflix as a Metro app.

Unlike Silverlight, Adobe Flash continues to maintain some relevance right now. YouTube continues to use Adobe Flash to serve FLV (at SD resolutions) and MP4 (at both SD and HD resolutions) streams. YouTube's debug OSD indicates whether hardware acceleration is being used or not.

Despite Windows 8 having plenty of YouTube apps, the browser interface is pretty much functional and free of external intrusive ads. The graph below shows the power consumption and GPU loading when playing a YouTube video in full screen using the Adobe Flash plugin on Mozilla Firefox.

The average GPU load is pretty constant around 8%, but power consumption at the wall has spikes corresponding to bursts of network activity. These bursts die down towards the end, after the full video gets buffered.

We saw that Haswell provided great power benefits for such network streaming activities in our HTPC piece at launch time. The Intel NUC takes this power benefit one step further by using a ULV processor. With a power consumption of less than 10 W for these activities, we are approaching dedicated media streamers' territory with the added flexibility of a full-blown PC at one's disposal.

The NUC as an HTPC

The form factor and network streaming power consumption profile of the Intel D54250WYK NUC makes it a very attractive option for HTPCs. We have already covered Haswell as a HTPC platform in great detail before. So, we will just take a look at a couple of interesting aspects which may vary from one build to another.

Refresh Rate Handling:

One of the most important fixes in Haswell for HTPC users was increased display refresh rate accuracy. We have already seen 23.976 Hz working perfectly in our custom Haswell HTPC build. The gallery below presents the various refresh rates that we tested out on the Intel D54250WYK NUC.

As expected, the refresh rate accuracy is excellent across all tested points. One of the pleasantly surprising aspect was that the drivers allowed forcing of refresh rates not reported by the display through EDID. This must have come in a recent update, because, when I was evaluating our first Haswell HTPC build, the i7-4765T based PC refused to drive 50 Hz on the Sony KDL46EX720. However, the NUC was able to do it successfully after deselecting 'Hide modes not supported by this monitor'.

Decoding and Rendering Benchmarks:

Detailed decoder / renderer benchmarks for Haswell were presented in our initial review. For the NUC, we are going to concentrate on XBMC's native decoding / rendering (used by the average HTPC user) and the combination of QuickSync with EVR-CP and madVR.

We used MPC-HC v1.7.1 for evaluation. LAV Filters 0.59.1.26 come pre-integrated as the default choice with that version. madVR 0.86.11 was configured with the following options: no decoding, deinterlacing automatically activated when needed with deactivation when in doubt (decided by only looking at pixels in the frame center), chroma upscaling set to bicubic with a sharpness of 75, image upscaling and downscaling done by GPU video logic using DXVA2 calls, rendering in full screen exclusive mode with playback delayed until fill up of the render queue, a separate device for presentation, CPU and GPU queue sizes of 128 and 24, 16 frames presented in advance, smooth motion features disabled and the default quality-performance tradeoffs of 16b pixel shader results and subtitle quality optimization for performance.

A number of experiments were done with different madVR settings and this was the one with which we were able to play all our test streams without frame drops. It must be noted that the streams benchmarked are meant to stress the system. The usual media file played back is more of the 1080p24 variety which goes comparatively easy on the resources compared to the 60 fps streams used for the tables below.

The only disappointing aspects above are related to the native decoder / renderer used by XBMC. Interlaced VC-1 decoding is broken when hardware accelerated decoding is enabled. Deinterlacing, particularly for the 480i60 stream, was not properly performed with any combination of settings. On the other hand, QuickSync decoding works smoothly (as expected) for all the test streams when used with any renderer.

Miscellaneous Factors and Concluding Remarks

Power Consumption:

We have already carried some graphs and tables with power consumption numbers for various scenarios in the preceding sections. The two graphs below compare idle and full load power consumption numbers across different low power desktops that we have evaluated before.

The Haswell NUC turns in stellar numbers for both scenarios. There is no doubt that this is a powerful, yet power-efficient, computing solution.

Thermal Performance:

The D54250WYK has an active cooling solution, but the size of the chassis is still a bit of a concern when it comes to cooling efficiency. To check the thermal performance of the kit, we let Prime 95 fully load up the CPU for 15 minutes, followed by the addition of Furmark to fully load the GPU also for the next 15 minutes. After this, the unit was left to idle while driving the display. Screenshots of the temperatures of various components (as reported by CPUID Hardware Monitor PRO) recorded at 15 minute intervals are presented in the gallery below.

At full CPU load, the temperatures of the cores reach 74 C, the fan spins at 3958 rpm (can go up to 4192 rpm) and the temperatures around the SSD (on the other side of the board) reach 43 C. With the GPU also fully loaded, the temperatures of the cores go down to around 67 C, the fan takes a little break at 3846 rpm. On the SSD side, the temperatures go a little further down to 41 C. After idling for 15 minutes after full loading, the cores are at 32 C, the fan is at 3206 rpm and the temperature on the SSD side goes down to 33 C. There is nothing to complain about with respect to the thermal solution except for the few notes about the fan noise that were made in the introduction.

Final Words:

From the HTPC perspective, it is troubling that HDMI audio still needs careful configuration in XBMC 12.3. For bitstreaming to work, XBMC has to be configured with WASAPI and not Direct Sound. The symptoms are the same as the Netflix HD audio issue. It is also a pity that interlaced VC-1 DXVA decoding doesn't work in XBMC. These are issues faced by the average consumer. We didn't touch upon the HDMI full range problem which HTPC enthusiasts treat as primary issue. All in all, it looks like Intel's graphics drivers still need to resolve lots of issues. While we have seen stellar progress over the last couple of years, it only leaves consumers asking for more to completely move away from discrete GPUs for HTPCs.

Moving away from the HTPC area, the NUC's low power consumption as well as small footprint enhance its appeal for use as thin clients or even full blown PCs for average office / home desktop use. The traditional desktop is being re-imagined in multiple ways with the advent of the touchscreen AiOs and form factors such as the NUC and the BRIX. The comparatively low cost and flexibility provided by the latter has ensured that the NUC form factor is here to stay as yet another excellent computing platform option for consumers.