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Intel Core i7-5775C: Broadwell for Desktops

Overshadowed by the Skylake launch, the delayed and mostly unavailable Core i7-5775C is an intriguing processor. Based on Broadwell, it sports backwards compatibility with LGA1150, a 65W TDP, an unlocked multiplier, 128MB of L4 cache, and turbo-charged Iris Pro 6200 graphics for the best desktop integrated graphics ever.

September 20, 2015 by Lawrence Lee

Product
Intel Core i7-5775C
LGA1150 Processor
Manufacturer
Street Price
US$390

The big story in computer hardware this summer was the release of Intel’s Skylake CPU microarchitecture, a long awaited platform update with a new socket and fresh chips for desktop systems. It’s a notable one if only for the fact that their last upgrade cycle, that saw a die shrink from 22 nm to 14 nm, initially skipped over desktop users completely. The plan for Broadwell was to focus on low power SKUs for the mobile/embedded market. Intel eventually announced a couple of 65W LGA1150 variants, seemingly as an afterthought. Unfortunately delays meant the Core i7-5775C and Core i5-5675C were not released until the Skylake launch was imminent.


Our Core i7-5775C sample.

CPU-Z screenshot.

 

Broadwell “C” vs. Haswell/Skylake “K” Processors
Model
i5-5675C
i5-4690K
i5-6600K
i7-5775C
i7-4770K
i7-4790K
i7-6700K
Socket
LGA1150
LGA1150
LGA1151
LGA1150
LGA1150
LGA1150
LGA1151
Memory Support
DDR3
DDR3
DDR3L
DDR4
DDR3
DDR3
DDR3
DDR3L
DDR4
Cores / Threads
4 / 4
4 / 4
4 / 4
4 / 8
4 / 8
4 / 8
4 / 8
CPU Clock (Base/Turbo)
3.1 / 3.6 GHz
3.5 / 3.9 GHz
3.5 / 3.9 GHz
3.3 / 3.7 GHz
3.5 / 3.9 GHz
4.0 / 4.4 GHz
4.0 / 4.2 GHz
L3 Cache
4MB
6MB
6MB
6MB
8MB
8MB
8MB
eDRAM/L4 Cache
128MB
128MB
Graphics
Iris Pro 6200
HD 4600
HD 530
Iris Pro 6200
HD 4600
HD 4600
HD 530
Execution Units
48
20
24
48
20
20
24
Max GPU Clock
1100 MHz
1200 MHz
1150 MHz
1150 MHz
1250 MHz
1250 MHz
1150 MHz
TDP
65W
88W
91W
65W
84W
88W
91W
Street Price (USD)
$280*
$230
$240
$390*
$330
$300
$355
* pre-order/out of stock pricing

Though obviously overshadowed by Skylake, these processors are more interesting for reasons beyond Intel’s poor timing. Broadwell was never intended for the desktop so they exhibit qualities of mobile chips. To hit the lower power envelope, clock speeds are lower than their Haswell counterparts, but bizarrely, they have unlocked CPU multipliers which makes them overclocking friendly. This defeats the purpose of having a 65W TDP as this limit undoubtedly needs to overruled to hit higher clock speeds.

There’s also a 2MB L3 cache penalty but hopefully this can be compensated for with 128MB of eDRAM that acts as L4 cache. This extra onboard memory can be accessed directly both by the CPU portion and by the pimped out integrated graphics. The two chips are armed with Iris Pro 6200 graphics which sport twice as many execution units (Intel’s equivalent of GPU cores) compared to the HD 530 graphics of the Skylake “K” models.

Suggested pricing is US$230 and US$350 for the i5-5675C and i7-5775C respectively, but with low initial stock and surprisingly high demand, it’s impossible to find any available for immediate purchase, resulting in prices being inflated by US$40~$50 at the minimum. And while they offer backwards compatibility with LGA1150 boards, it’s limited to 9-series chipset models, assuming the manufacturer offers the necessary BIOS update.

TEST METHODOLOGY

Motherboards:

  • Gigabyte Z170X-UD5 – LGA1151, Z170 chipset, ATX
  • Gigabyte Z97MX-Gaming 5 – LGA1150, Z97 chipset, microATX
  • Asus Sabertooth 990FX R2.0 – AM3+ socket, 990FX chipset, ATX
  • ASRock FM2A88-ITX+ – FM2+ socket, A88X chipset, mini-ITX
  • Asus F2A85-M Pro – FM2 socket, A85X chipset, microATX

Common Test Components:

  • Kingston
    HyperX Genesis memory
    – 2x4GB, DDR3-1866 @ 1600 MHz, C9
  • Kingston Fury memory – 2x4GB, DDR4-2667, C15
  • Seasonic
    SS-400ET
    power supply – 400W, ATX
  • Scythe Kabuto
    CPU cooler – stock fan at 800 RPM
  • Microsoft
    Windows 7
    operating system – Ultimate, 64-bit

IGP Only Test Components:

  • ADATA XPG SX910 128GB or Kingston HyperX 3K 120GB solid-state drive – 2.5-inch, SATA 6 Gbps

CPU Only Test Components:

  • Asus EN9400GT Silent Edition
    graphics card – 512MB
  • Western Digital VelociRaptor
    hard drive – 300GB, 10,000RPM, 16MB cache

IGP test platform device listing.

Measurement and Analysis Tools:

Timed Benchmark Test Details:

  • Photoshop: Image manipulation using a variety of filters, a derivation
    of Driver Heaven’s Photoshop
    Benchmark V3
    (test image resized to 4500×3499).
  • NOD32: In-depth virus scan of a folder containing 32 files of varying
    size with many 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: Encoding a XVID AVI file with VC-1.
  • HandBrake: Encoding a XVID AVI file with H.264.

Gaming Performance Benchmarks:

Video Test Suite:


1080p | 24fps | ~22 mbps

H.264/MKV: A custom 1080p H.264 encoded clip inside an Matroska container.

 


1080p | 24fps | ~2.3 mbps

Flash 1080p: The Dark Knight Rises Official Trailer #3, a YouTube HD trailer in 1080p.

Testing Procedures

Our main test procedure is a series of both CPU (timed tests of real-world applications) and GPU-centric (gaming tests and synthetics) benchmarks. System power consumption is measured during the CPU tests (an average of the first 5~15 seconds) and in various states including idle, H.264 and Flash playback and full CPU and GPU load using Prime95/CPUBurn and FurMark.

Certain services and features like Superfetch and System Restore are disabled
to prevent them from affecting our results.
We also make note if energy saving features like Cool’n’Quiet and SpeedStep
do not function properly.

Estimating DC Power

The following power efficiency figures were obtained for the
Seasonic SS-400ET used in our test system:

Seasonic SS-400ET Test Results
DC Output (W)
21.2
41.6
60.2
81.9
104.7
124.1
145.2
AC Input (W)
32.0
58.0
78.0
102.0
128.0
150.0
175.0
Efficiency
66.3%
71.7%
77.1%
80.3%
81.8%
82.8%
83.0%

This data is enough to give us a very good estimate of DC demand in our
test system. We extrapolate the DC power output from the measured AC power
input based on this data. We won’t go through the math; it’s easy enough
to figure out for yourself if you really want to.

TEST RESULTS: INTEGRATED GRAPHICS

Energy Efficiency

Running off integrated graphics, the i7-5775C is on par with Haswell chips when it comes to power consumption during light load, shaving a couple of watts off at idle, but using a similar amount rendering Flash and H.264 video.

The i7-5775C has a slight efficiency advantage compared to the i5-4670K and i7-4770K on heavy CPU load but keep in mind it runs at a lower clock speed (3.7 GHz with Turbo Boost). However when its turbo-charged integrated graphics is put to the test in Crysis, the system pulls over 100W AC, substantially more than lower tier Haswell solutions.

The Prime95 stress test brings the chip close to its power limit as adding FurMark to the mix only results in a 1W increase. The 65W TDP seems to prevent either the CPU or GPU from its full potential depending on which is in greater demand. Raising the power limits in the BIOS allows the CPU to hit higher multipliers but when the GPU is stressed as well, the power draw still will not exceed 107W. The power consumption difference between Prime95 and Prime95 + FurMark when the CPU set to its minimum 800 MHz is 54W, so the system could theoretically pull ~160W if not constrained by the TDP.

The implication is that the CPU clock speed will throttle down during GPU-intensive tasks to abide the power limit. I can confirm this as the CPU clock speed was observed running between below 2.0 GHz during our gaming tests (the Haswell processors run at full speed). Thankfully this doesn’t affect any of our gaming benchmarks as they are primarily GPU-dependent. With CPU-limited titles, you should expect a performance penalty.

Gaming Performance

Our real world gaming tests is conducted at two resolutions, 1366×768 and 1600×900 (or whatever is the closest valid resolution available), with differing levels of image quality. The results we report are for the highest resolution and detail level with which the product can deliver a reasonably good framerate (about 45 frames per second). Integrated graphics from Intel and AMD are depicted in blue and red respectively while discrete graphics has been assigned purple.

For the past couple of years, we’ve only compared integrated graphics to other integrated models and a single discrete card, a Radeon HD 6570 (equivalent to a US$40 model these days), and only using modest screen resolutions. That has to change with Iris Pro 6200 as it simply knocks them all out of the water. It plays all of our tests well at ~1600×900, sometimes putting out twice the average framerate of the HD 4600. It’s also significantly faster than the last generation of Iris Pro graphics found on the i7-4770R.

We arrived at our overall gaming performance rating by giving each GPU a proportional
score in each gaming benchmark with each test having an equal weighting.
The scale has been adjusted so that the i7-6700K’s HD 530 graphics (Skylake) is the reference point with
a score of 100.

Overall there is a 90% improvement compared to the new i7-6700K. It’s even more impressive against Haswell with the i7-5775C doubling the performance of the i7-4770K.

Iris Pro 6200 sets itself apart as the first integrated graphics solution that can handle all of our benchmarks comfortably at 1080p resolution. As such, it’s deserving of better competition, a trio of older discrete cards, the Radeon HD 7750, GeForce GTS 450 and GeForce GT 640. The same CPU was used for the Nvidia cards while the AMD model was tested with our Skylake platform as it inexplicably wouldn’t boot with our Z97 board. This won’t matter as none of these games are CPU-bound with this class of processor.

To our surprise, it renders our most demanding game, Aliens vs. Predator with the best average framerate and also posts strong results in Just Cause 2 and Resident Evil 5. Its performance is noticeably superior to the Zotac GT 640 ZONE which is paired with DDR3 memory. If I had to guess, I would estimate it’s on par with the GDDR5 version of the same model, or its successor, the GT 740, which can be found for as low as US$70.

Gaming with the integrated graphics isn’t necessarily more power efficient either as the system power consumption of the Iris Pro 6200 machine is consistantly over 100W, more than both the GT 640 and HD 7750 configurations.

TEST RESULTS: DISCRETE GRAPHICS

The bulk of our CPU testing was conducted with a discrete graphics card (a GeForce 9400 GT) to eliminate integrated graphics as a variable, most notably with regards to power consumption. It’s also necessary to fairly compare CPUs that do not have an onboard graphics chip such as AMD FX models.

CPU Performance

In most of our tests, the i7-5775C is just a hair’s breath away from the i7-4770K. It’s also more power efficient in every task, especially the more demanding video encoding applications. It even manages to post the best ever result in our file compression test as WinRAR is heavily memory dependent and the i5-5775C’s extra cache gives it a distinct advantage.

You may have noticed that the A8-7600 has been thrown in along with the other competitors despite being a sub-US$100 APU. It’s not in the same performance class of course but it’s currently AMD’s only widely available quad core chip with a 65W TDP. Despite this, it too, failed to draw less power than the i7-5775C.

We arrived at our overall performance figures by giving each CPU a proportional
score in each real world benchmark with each test having an equal weighting.
The scale has been adjusted so that the popular Core i5-4690K is the reference point with
a score of 100.

Despite a disadvantage in clock speed, the new architecture and the extra cache on board allows the i7-5775 to slip past the i7-4770K by a margin of 6%.

Energy Efficiency

Using discrete graphics, the overall power consumption dynamic evens out between Skylake and Broadwell.

For users with balanced workloads, we’ve determined what we call the “average power consumption” which assumes the system is used half the time for light load activities (an average of idle and H.264 playback) and the remaining half for heavy load (an average of the power consumption used running our six benchmarks). We believe this is a very common usage pattern for an average PC — they are often left on for long periods of time, doing little to no work.

In this scenario, the i7-5775C is supreme, edging out the i7-6700K by about 1W.

For users with heavy workloads, the total power consumed while running our benchmark suite is of pertinent interest. The total power takes into account the energy efficiency of each CPU while running our benchmark tests as well as how quickly they complete each task. This simulates the power draw of a machine that is purely for doing work and shuts down when its job is finished.

As a total workhorse processor, the i7-5775C trails only the i7-6700K by a mere 0.4 Wh or 5%.

To determine performance per watt, we took our relative CPU performance figures and divided it by the “average” power consumption calculated earlier and adjusted the scale so the i5-4690K would act again as our standard with 100 points.

The i7-5775C and i7-6700K deliver similar levels of energy efficiency but the Skylake chip is somewhat faster, giving it the edge in performance per watt.

Value Analysis

When considering the cost of a system, the CPU is only part of the equation
as the price of motherboards and RAM must be added to find the true platform price. n the
chart above, we included the prices of the chips compared today (that are still widely available and not obsolete due to EOL), 8GB of RAM (DDR4 for Skylake as it’s more commonly supported), and an average compatible motherboard from Newegg
that fulfill this basic barebones set of criteria:

  • Retail models
  • In stock
  • Not extravagantly priced (most expensive models omitted)
  • Major name brand (ASRock, Asus, Intel, Gigabyte, MSI)
  • SATA 6 Gbps support in some form
  • USB 3.0 support in some form

The i7-5775C is in short supply so the market price is currently much higher than what Intel suggests. No retailer had them in stock at time of writing, with pre-orders open at a few sites for US$380~$400. As Broadwell parts are only compatible with 9-series chipsets (with a BIOS update), the average motherboard cost is also US$20 higher than Haswell. This offsets the price premium of DDR4 memory, so the overall cost of such a platform is similar to a Skylake i7-6700K configuration.

To calculate performance per dollar, we divided the relative performance scores by the platform costs and re-scaled it, again with the i5-4670K as our reference point. We don’t have test data on the i7-4790K, but it’s significant enough to place on the chart as it is both cheaper and runs at a faster clock speed than the i7-4770K.

Taking into consideration CPU performance alone, the i7-5775C doesn’t give you a whole lot for your money. We’ve already determined that the i7-6700K offers better performance per watt, so you really need to take advantage of its beefy integrated graphics to receive some semblance of value.

To adjust the performance per dollar for GPU performance, the cost of an Iris Pro 6200 equivalent (US$70) graphics card has been tacked on to all non-Broadwell chips.

Even if you discount the worth of lower-tier Intel graphics altogether, the i7-5775C only offers more value than the outdated/overpriced Core i7-4770K and new Skylake Core i7. Both of the Haswell Refresh models, the i7-4790K and i5-4690K, deliver more bang for your buck if you pair it with a comparable dedicated video card.

FINAL THOUGHTS

The Core i7-5775C is an odd duck, not only because it’s the first Broadwell processor for the desktop. It’s a specialty part that bizarrely melds together an unlocked CPU multiplier, a low 65W TDP, L4 cache, and a graphics chip that absolutely dominates all integrated solutions as well as a sizable proportion of low-end discrete graphics cards. On paper it looks like a pretty good value, especially given its backwards compatibility with LGA1150/9-series motherboards.

Unfortunately due to supply and demand driving the price up, you can purchase a Haswell configuration with a comparable video card that will perform similarly in most respects for significantly less, and even a Skylake i7-6700K system offers more overall value. The Iris Pro 6200 graphics is its biggest selling point, and while it is formidable, it too has its limitations. If you ever decide to upgrade to a discrete card, it will be placed on the sidelines with its talents being wasted. Users who are drawn to the “green” aspect of Broadwell should note that while it is more energy efficient than Haswell, the difference is slight on the desktop despite what the TDP rating suggests.

The i7-5775C is essentially a mobile chip ported to the desktop space, trying to offer everything in one package. With a desktop socket, users have choice, so it’s generally preferable to specialize. I’m all for a power-sipping Broadwell, an unlocked Broadwell for overclocking to the moon, and a Broadwell with tremendous built-in graphics, but all of them jammed into the same package isn’t a great strategy. The i7-5775C is the most interesting desktop CPU of the past few years but ultimately it struggles to find a purpose within Intel’s LGA1150 lineup.

Our thanks to Intel for the Intel Core i7-5775C processor sample.

* * *

Articles of Related Interest
Skylake: Intel Core i7-6700K
AMD Kabini: Athlon 5350 Desktop SoC
AMD A8-7600 Kaveri APU
AMD A10-6800K & A10-6700 Richland APUs
Intel Core i7-4770K Haswell Processor
AMD FX-8350 CPU: Piledriver Arrives

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