Introduction and Setup Impressions

Over the last couple of years, mini-PCs in the ultra-compact form factor (UCFF) have emerged as one of the bright spots in the troubled PC market. Intel's NUC systems are one of the most popular in this category. The lack of graphic prowess in the NUCs allowed for machines such as BRIX Pro (based on the Haswell Iris Pro CPU) to enter the market. With Broadwell, Intel is bringing out an Iris NUC on its own.

The 14nm Broadwell CPUs were introduced into the market with the Core M branding for fanless ultraportables. Essentially a rebranding of Y-series CPUs, its power efficiency got everyone excited about what a higher TDP version (U-series) could bring for the PC market. Even as ultrabooks based on Broadwell-U are getting ready for the market, Intel and its partners have started getting the UCFF units into the hands of consumers. Intel's Broadwell NUCs were introduced at CES 2015. We have already reviewed GIGABYTE's Core i7-5550U-based BRIX s and Intel's own Core i5-5250U-based NUC5i5RYK units, giving us some insight into how a 15 W TDP Broadwell-U might perform for common workloads. With Intel's partners launching UCFF PCs based on the U-series CPUs, it was always going to be interesting to see how they could differentiate their Broadwell NUCs. This review of the NUC5i7RYH - Intel's Core i7 Broadwell-U-based NUC with Iris Graphics 6100 - provides some insights.

Traditionally, the NUCs are barebones machines - the end-user could choose an appropriate mSATA SSD (or, for selected models, 2.5" drives), a mini-PCIe WLAN adapter, DDR3L SO-DIMMs and an operating system. Intel has two main changes in the barebones approach for the Broadwell-U NUCs: The WLAN adapter (Intel AC7265) now comes soldered to the motherboard. mSATA SSDs are no longer supported. In its place, we have support for either SATA or PCIe-based M.2 SSDs. Similar to the previous generation NUCs, a free SATA port is available on the board. The Iris NUC is sized to accommodate a 2.5' drive also. The SATA data and power cables are already routed and the appropriate chassis slots are in place to make adding a 2.5" drive very easy (as can be seen in the photograph below).

Intel also supplied us with a sample of Samsung's SM951 M.2 NVMe drive for use as the primary storage medium. The specifications of our Intel NUC5i7RYH review configuration are summarized in the table below.

Intel NUC5i7RYH Specifications
Processor	Intel Core i7-5557U (2C/4T x 3.1 GHz, 14nm, 4MB L2, 28W TDP)
Memory	2x 8GB DDR3L-1866 C13
Graphics	Intel Iris Graphics 6100
Disk Drive(s)	Samsung SM951 Series MZVPV256 256 GB M.2 NVMe SSD
Networking	1x Intel I218-V GbE, 2x2 Intel AC7265 802.11ac Wi-Fi
Audio	Capable of 5.1/7.1 digital output with HD audio bitstreaming (HDMI)
Operating System	Retail unit is barebones, but we installed Windows 8.1 Pro x64
Pricing (As configured)	$878
Full Specifications	Intel NUC5i7RYH Specifications

The Intel NUC5i7RYH kit doesn't come with any pre-installed OS, but our pre-production engineering sample review unit came with a USB key containing the drivers. In addition to the main unit, the other components of the package include a 65 W (19V @ 3.43A) wall-wart (with detachable multi-country power plugs), a VESA mount (along with the necessary screws), setup guides and a QVL (qualified vendors list) for the memory and storage subsystems. The gallery below takes us around the chassis. The Wi-Fi module is underneath the M.2 SSD and not visible in the gallery photo.

The Iris NUC officially supports DDR3L SO-DIMMs at 1600 MHz. However, the BIOS automatically configures the memory for the highest possible speed. Our Crucial DIMM kits support running at up to 1866 MHz and they were automatically configured to run at that frequency with timings of 13-13-13-32 - this is much worse than the usual 1866 MHz kits that we have access to. However, given that memory overclocking is automatically configured, we evaluated the system with those timings.

In the table below, we have an overview of the various systems that we are comparing the Intel NUC5i7RYH against. Note that they may not belong to the same market segment. The relevant configuration details of the machines are provided so that readers have an understanding of why some benchmark numbers are skewed for or against the Intel NUC5i7RYH when we come to those sections.

Comparative PC Configurations
Aspect	Intel NUC5i7RYH	Intel NUC5i7RYHGIGABYTE GB-BXi7H-5500GIGABYTE GB-BXi7-4770R (2)GIGABYTE GB-BXi7-4500Intel NUC5i5RYK (Enthusiast)Intel D54250WYKH
CPU	Intel Core i7-5557U	Intel Core i7-5557U
GPU	Intel Iris Graphics 6100 (Broadwell-H GT3)	Intel Iris Graphics 6100 (Broadwell-H GT3)
RAM	Crucial CT102464BF186D.M16 13-13-13-32 @ 1866 MHz 2x8 GB	Crucial CT102464BF186D.M16 13-13-13-32 @ 1866 MHz 2x8 GB
Storage	Samsung SM951 Series MZVPV256 (256 GB; M.2 Type 2280 PCIe 3.0 x4 NVMe; 19nm; MLC)	Samsung SM951 Series MZVPV256 (256 GB; M.2 Type 2280 PCIe 3.0 x4 NVMe; 19nm; MLC)
Wi-Fi	Intel Dual Band Wireless-AC 7265 (2x2 802.11ac - 867 Mbps)	Intel Dual Band Wireless-AC 7265 (2x2 802.11ac - 867 Mbps)
Price (in USD, when built)	$878	$878

Performance Metrics - I

The Intel NUC5i7RYH was evaluated using our standard test suite for low power desktops / industrial PCs. We revamped our benchmark suite early last year after the publication of the Intel D54250WYK NUC review. We reran some of the new benchmarks on the older PCs also, but some of them couldn't be run on loaner samples. Therefore, the list of PCs in each graph might not be the same.

Futuremark PCMark 8

PCMark 8 provides various usage scenarios (home, creative and work) and offers ways to benchmark both baseline (CPU-only) as well as OpenCL accelerated (CPU + GPU) performance. We benchmarked select PCs for the OpenCL accelerated performance in all three usage scenarios. These scores are heavily influenced by the CPU in the system as well as the RAM speed. Even though the Core i7-5557U in the NUC5i7RYH is not as powerful as the Core i7-4770R in the BRIX Pro, we find that the scores are neck and neck, with the former even edging out the more powerful variant (possibly due to differences in the OpenCL drivers that they were tested with).

Miscellaneous Futuremark Benchmarks

In the other Futuremark benchmarks, the relative performance is as expected - the Core i7-4770R leads the pack, followed by the Core i7-5557U in the NUC5i7RYH. This trend is also present in the CINEBENCH results discussed below.

3D Rendering - CINEBENCH R15

We have moved on from R11.5 to R15 for 3D rendering evaluation. CINEBENCH R15 provides three benchmark modes - OpenGL, single threaded and multi-threaded. Evaluation of select PCs in all three modes provided us the following results.

Performance Metrics - II

In this section, we mainly look at benchmark modes in programs used on a day-to-day basis, i.e, application performance and not synthetic workloads.

x264 Benchmark

First off, we have some video encoding benchmarks courtesy of x264 HD Benchmark v5.0. This is simply a test of CPU performance. As expected, the Core i7-5557U performs much better than any other U-series CPU that we have tested so far. Thanks to its high TDP, it can sustain higher clock rates. Obviously, it is no match for the 65W TDP Core i7-4770R in the BRIX Pro.

7-Zip

7-Zip is a very effective and efficient compression program, often beating out OpenCL accelerated commercial programs in benchmarks even while using just the CPU power. 7-Zip has a benchmarking program that provides tons of details regarding the underlying CPU's efficiency. In this subsection, we are interested in the compression and decompression MIPS ratings when utilizing all the available threads.

TrueCrypt

As businesses (and even home consumers) become more security conscious, the importance of encryption can't be overstated. CPUs supporting the AES-NI instruction for accelerating the encryption and decryption processes have, till now, been the higher end SKUs. However, with Bay Trail, even the lowly Atom series has gained support for AES-NI. The Core i7-5557U in the NUC5i7RYH does have AES-NI support. TrueCrypt, a popular open-source disk encryption program can take advantage of the AES-NI capabilities. The TrueCrypt internal benchmark provides some interesting cryptography-related numbers to ponder. In the graph below, we can get an idea of how fast a TrueCrypt volume would behave in the Intel NUC5i7RYH and how it would compare with other select PCs. This is a purely CPU feature / clock speed based test.

Agisoft Photoscan

Agisoft PhotoScan is a commercial program that converts 2D images into 3D point maps, meshes and textures. The program designers sent us a command line version in order to evaluate the efficiency of various systems that go under our review scanner. The command line version has two benchmark modes, one using the CPU and the other using both the CPU and GPU (via OpenCL). The benchmark takes around 50 photographs and does four stages of computation:

• Stage 1: Align Photographs
• Stage 2: Build Point Cloud (capable of OpenCL acceleration)
• Stage 3: Build Mesh
• Stage 4: Build Textures

We record the time taken for each stage. Since various elements of the software are single threaded, others multithreaded, and some use GPUs, it is interesting to record the effects of CPU generations, speeds, number of cores, DRAM parameters and the GPU using this software.

Dolphin Emulator

Wrapping up our application benchmark numbers is the Dolphin Emulator benchmark mode results. This is again a test of the CPU capabilities, and the trend observed in the previous benchmarks in this section get repeated here. The Core i7-5557U is simply the highest-performing U-series CPU that we have evaluated so far.

Gaming Benchmarks

Intel's integrated GPUs don't have a big name in the gaming community. Once in a while, Intel throws in a surprise. In the Haswell family, CPUs with Iris Pro graphics gave a pleasant surprise to casual gamers. In this section, we will identify whether the Intel Iris Graphics 6100 in the Core i7-5557U can provide an acceptable gaming experience. It will also be interesting to find out how it compares against the HD 6000 in the Core i5-5250U and the HD 5500 inthe Core i7-5500U (BRIX s).

For the purpose of benchmarking, we chose four different games (Sleeping Dogs, Tomb Raider, Bioshock Infinite and DiRT Showdown) at three different quality levels. As someone focusing on HTPCs and multimedia aspects, I rarely get to process gaming benchmarks, even while evaluating GPUs. One of the aspects that I feared was spending lot of time in installing the same games again and again on different PCs under the review scanner. The solution was to go the Steam route. Unfortunately, Steam also likes to keep the game files updated. A quick online search revealed that Steam could make use of an external drive for storing the game executables and downloadable content. With the Steam drive on-the-go use-case being read-heavy, the Corsair Flash Voyager GS USB 3.0 128GB Flash Drive (with read speeds of up to 275 MBps) was ideal for use as a portable Steam drive.

Sleeping Dogs

Tomb Raider

Bioshock Infinite

DiRT Showdown

At lower quality levels, the HD 5500 in the Core i7-5500U can sometimes provide marginally better frame rates, but the Iris Graphics 6100 trumps other UCFF PCs in almost all other situations. The only exception is the Core i7-4770R-equipped BRIX Pro that is also equipped with Iris Pro Graphics. Despite belonging to the previous generation, the higher TDP (65W vs. 28W) allows for better GPU performance.However, at the 20W and lower TDP-point / acoustic profile / chassis size, it goes without saying that Iris Graphics 6100 possesses the best gaming credentials.

Networking and Storage Performance

We have recently started devoting a separate section to analyze the storage and networking credentials of the units under review. On the storage side, one option would be repetition of our strenuous SSD review tests on the drive(s) in the PC. Fortunately, to avoid that overkill, PCMark 8 has a storage bench where certain common workloads such as loading games and document processing are replayed on the target drive. Results are presented in two forms, one being a benchmark number and the other, a bandwidth figure. We ran the PCMark 8 storage bench on selected PCs and the results are presented below.

The MZVPV256 is the first NVMe SSD in the M.2 form factor. Given its PCIe 2.0 x4 link (the controller supports PCIe 3.0, but the unit connects to the PCIe 2.0 lanes in the Broadwell-U package) and the advantages of NVMe over AHCI, we expected our configuration to lead the storage charts. Our unexpected results made us run a couple of other artificial benchmarks (reproduced below).

The results from ATTO and CrystalDiskMark matches the specifications (accounting for the downgrade of the host link from PCIe 3.0 to PCIe 2.0). After discussion with Samsung, it turned out that the performance difference was due to the Microsoft NVMe driver creating FUA (Force Unit Access) I/O write commands. These FUA commands bypass the DRAM cache on the SSD and directly write to the flash, increasing the response time and also lowering bandwidth. For the same access traces, this situation does not happen with the Microsoft AHCI driver.

We observed something similar with the Intel SSD P3700 NVMe PCIe drive. With the Microsoft NVMe driver, the benchmark reported storage bandwidth around 320 MBps, while the Intel NVMe driver bumped that upwards of 500 MBps. So, we can conclude with a high degree of confidence that the Microsoft NVMe driver needs some fixes.

On the networking side, we restricted ourselves to the evaluation of the WLAN component. 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 a typical US building). A wired client (Zotac ID89-Plus) is connected to the R7000 and serves as one endpoint for iPerf evaluation. The PC under test is made to connect to either the 5 GHz (preferred) or 2.4 GHz SSID and iPerf tests are conducted for both TCP and UDP transfers. It is ensured that the PC under test is the only wireless client for the Netgear R7000. We evaluate total throughput for up to 32 simultaneous TCP connections using iPerf and present the highest number in the graph below.

In the UDP case, we try to transfer data at the highest rate possible for which we get less than 1% packet loss.

Recent driver updates have enabled the Intel AC726x solutions to perform up to their advertised potential. Users facing issues with them are urged to update their drivers as well as router firmware in order to take advantage of the capabilities. The Broadwell-U NUC (NUC5i5RYK) uses the same Intel AC-7265 2x2 802.11ac soldered M.2 Wi-Fi card as the NUC5i7RYH. So, it is not surprising that the TCP and UDP throughputs are similar for the two systems.

HTPC Credentials

The NUC5i7RYH is a UCFF PC, but, thanks to the 28W TDP CPU inside, the thermal solution required is a bit more noisy compared to what we saw in the NUC5i5RYK. Subjectively speaking, the unit is silent for most common HTPC use-cases. Only under heavy CPU / GPU loading (such as stressful madVR configurations) does the fan become audible. In our investigation, recent software improvements in the software chain for playback on Windows have lightened the stress considerably. The NUC5i7RYH definitely makes a good HTPC for folks who don't want to pay the premium for a passively cooled system - however, we didn't find too many improvements over the NUC5i5RYK for HTPC workloads. The Iris NUC also has CIR support enabling use of IR remotes in a home theater setting.

Refresh Rate Accurancy

Starting with Haswell, Intel, AMD and NVIDIA have been on par with respect to display refresh rate accuracy. The most important refresh rate for videophiles is obviously 23.976 Hz (the 23 Hz setting). As expected, the Intel NUC5i7RYH has no trouble with refreshing the display appropriately in this setting.

The gallery below presents some of the other refresh rates that we tested out. The first statistic in madVR's OSD indicates the display refresh rate.

Network Streaming Efficiency

Evaluation of OTT playback efficiency was done by playing back our standard YouTube test stream and five minutes from our standard Netflix test title. Using HTML5, the YouTube stream plays back a 720p encoding. Since YouTube now defaults to HTML5 for video playback, we have stopped evaluating Adobe Flash acceleration. Note that only NVIDIA exposes GPU and VPU loads separately. Both Intel and AMD bundle the decoder load along with the GPU load. The following two graphs show the power consumption at the wall for playback of the HTML5 stream in Mozilla Firefox (v 37.0.1).

GPU load was around 12.58% for the YouTube HTML5 stream and 2.41% for the steady state 6 Mbps Netflix streaming case.

Netflix streaming evaluation was done using the Windows 8.1 Netflix app. Manual stream selection is available (Ctrl-Alt-Shift-S) and debug information / statistics can also be viewed (Ctrl-Alt-Shift-D). Statistics collected for the YouTube streaming experiment were also collected here.

Surprisingly, the Iris NUC emerges as the most power-efficient configuration for OTT streaming amongst the configurations compared above. The mainstream NUC5i5RYK build (using slower DRAM and a M.2 SATA SSD) is more power efficient for OTT streaming, but those numbers are not presented in the graphs above. Thie observed numbers could be due to a number of factors - software and driver updates as well as more power efficient components inside the build.

Decoding and Rendering Benchmarks

In order to evaluate local file playback, we concentrate on EVR-CP and madVR using the mainstream configuration (which has the 1600 MHz DRAM). We already know that EVR works quite well even with the Intel IGP for our test streams. In our Broadwell BRIX s review, we found the HD Graphics 5500 to be incapable of downscaling 4kp30 to 1080p using default madVR settings. Could Iris / Iris Graphics 6100 help in this aspect? Have software updates to LAV Filters (0.64.0) and madVR (0.87.1) delivered increased playback efficiency? Our experimental results presented below provide the answers.

In our earlier reviews, we focused on presenting the GPU loading and power consumption at the wall in a table (with problematic streams in bold). Starting with the Broadwell NUC review, we decided to represent the GPU load and power consumption in a graph with dual Y-axes. Nine different test streams of 90 seconds each were played back with a gap of 30 seconds between each of them. The characteristics of each stream are annotated at the bottom of the graph. Note that the GPU usage is graphed in red and needs to be considered against the left axis, while the at-wall power consumption is graphed in green and needs to be considered against the right axis.

Frame drops are evident whenever the GPU load consistently stays above the 85 - 90% mark. In addition to tracking that aspect in the graphs below, we also get an idea of the system's power efficiency for decode and playback of some common codecs.

EVR-CP doesn't present any challenges to the Iris Graphics 6100

Iris Graphics 6100 still struggles with 4Kp30 downscaling to 1080p with madVR's default settings

In addition to the above configurations, we also set up a 'madVR stress configuration' with the upscaling algorithms set to Jinc 3-tap with anti-ringing activated and the downscaling algorithm set to Lanczos 3-tap, again with anti-ringing activated.

Iris Graphics 6100 is unable to handle luma scaling with our madVR stress settings

We find that all streams that involve luma scaling for display on a 1080p screen (interlaced standard definition and progressive high definition as well as ultra high definition) consistently loaded up the GPU above 95% and plenty of dropped frames during playback.

The Iris Graphics 6100 is a definite step-up over the HD Graphics 6000. However, the improvements for HTPC workloads are marginal at best. The NUC5i7RYH Iris NUC can only be recommended if a UCFF PC is desired for light gaming in addition to HTPC workloads.

Power Consumption and Thermal Performance

The power consumption at the wall was measured with a 1080p display being driven through the HDMI port. In the graphs below, we compare the idle and load power of the Intel NUC5i7RYH with other low power PCs evaluated before. For load power consumption, we ran Furmark 1.12.0 and Prime95 v27.9 together. The numbers are not beyond the realm of reason for the combination of hardware components in the machine.

In the steady state, the clocks are managed in order to ensure that the at-wall power consumption stays within the limits of the thermal design's capabilities. As we will see further down, the unit can consume more than 55 W at the wall for short bursts before the thermal management kicks in.

Our thermal stress routine starts with the system at idle, followed by 30 minutes of pure CPU loading. This is followed by another 30 minutes of both CPU and GPU being loaded simultaneously. After this, the CPU load gets removed, allowing the GPU to be loaded alone for another 30 minutes. The various clocks in the system as well as the temperatures within the unit are presented below.

According to Intel's official specifications, the junction temperature of the Core i7-5557U is 105C. We find that pure CPU loading takes us close to it with turbo frequencies (3.4 GHz). However, before thermal throttling can kick in, the CPU cores revert to the rated operating frequency of 3.1 GHz. At that frequency, the cores have no trouble staying below the junction temperature.

The case of CPU and GPU getting loaded simultaneously is more interesting. The CPU cores run at 1.5 GHz and the GPU around 750 MHz. The temperature of the CPU package doesn't go above 85 C in this scenario. Obviously, we are not being thermally limited. The at-wall power consumption graph provides more insight.

The limiting factor on the performance / operating frequencies turns out to be the at-wall power consumption. With both CPU and GPU loaded simultaneously, the unit has a sustained power consumption of around 45 W, and we find that the number is similar for both the CPU-only and GPU-only scenarios.

On the whole the thermal design works well. As long as the limiting factors for the performance of the NUC are understood, the end users should not be in for any surprises.

 

Final Words

The Intel NUC5i7RYH provided us with the opportunity to take a look at what a higher TDP CPU and Iris Graphics can bring to the table in the UCFF space. Intel is pitching the Iris NUC as a gaming and content creation solution. Based on our evaluation, the Iris NUC seems to provide the best performance per watt in this form factor. The BRIX Pro with the Core i7-4770R is a better all-round solution, but that comes with bad acoustics and higher power consumption. It is also slightly bigger in order to accommodate the necessary thermal solution. The Iris NUC doesn't suffer from those drawbacks, thanks to the use of a 28W TDP CPU in the system.

In terms of scope for improvement, we would like to see a full-sized HDMI port in the back panel. The BRIX PCs are able to accommodate full-sized HDMI ports, so there is really nothing on the technical side to prevent this. If a mini-HDMI port is non-negotiable, it would be good to have either a mini-HDMI to full-sized HDMI adapter or a mini-HDMI to HDMI cable in the package. The design for accommodating the 2.5" drive is better than what we saw in the Haswell NUC. However, the cabling and 2.5" drive slot in the BRIX H series is definitely better. Other improvement aspects that we suggested in the Broadwell-U NUC review are applicable here also.

Minor quibbles aside, the Iris NUC delivers what it promises - decent casual gaming credentials and optimal CPU performance while ensuring that acoustics and power consumption remain reasonable. In fact, it has the best performance amongst all the traditional UCFF PCs that we have evaluated so far.

The final aspect that we talk about today is pricing. The NUC5i7RYH seems to be available on pre-order for $480 on CDW (even though Intel indicated a street price of $500). M.2 SSDs (both NVMe and SATA AHCI) continue to carry a premium. For users wishing to keep the build cost down, the Iris NUC also supports a traditional 2.5" drive. This makes the Iris NUC mini-PC an excellent choice for all budgets.