PC enthusiasts have a proud tradition of appropriating enterprise-class hardware for personal systems. Stuffing server-grade gear into a desktop can improve performance dramatically in some cases. It also unlocks immediate bragging rights over systems equipped with more pedestrian hardware.
Although hardware makers tend to frown at this practice, some have adopted it as their own. Intel, for example, has long fueled its high-end desktop platform with parts pulled from the server and workstation world. Haswell-E and its predecessors are really just Xeon CPUs repurposed for desktop use—and packaged specifically with enthusiasts in mind. The company’s storage division has been getting in on the action, too. Last year, it introduced a 730 Series SSD that’s basically a rebadged datacenter drive with a few tweaks under the hood.
The 730 Series is pretty sweet, but it’s tied to a Serial ATA interface and AHCI protocol that can’t keep up with modern flash memory. That’s why Intel’s latest datacenter drives use a faster PCI Express interface backed by an SSD-specific NVM Express protocol. This new family hit servers last summer, and today, it migrates to the desktop as the 750 Series.
Under the hood, the 750 Series features the same controller as its datacenter counterparts. This proprietary Intel chip has an eight-channel NAND interface at one end and four lanes of PCIe Gen3 goodness at the other. It’s meant to connect directly to PCIe lanes in the CPU rather than through an intermediary chipset on the motherboard. (Intel’s 9-series chipsets are limited to Gen2 speeds, so they’re not fast enough to keep up.)
Four lanes of PCIe Gen3 connectivity offer up to 4GB/s of theoretical bandwidth, which is well above SATA’s top speed—and comfortably beyond the bandwidth of the dual-Gen2 M.2 slots on most motherboards. A wider pipe is only one piece of the puzzle, though. The controller is also based on the NVM Express protocol designed to replace SATA’s ancient AHCI spec.
AHCI was architected for hard drives based on mechanical platters. Those drives are a low-speed, high-latency proposition compared to the massively parallel NAND arrays behind modern SSDs. NVMe was designed from the ground up for solid-state storage, so it lacks legacy baggage from the mechanical era. It promises better performance through lower overhead and greater scalability. Where AHCI is limited to a single command queue 32 entries deep, NVMe supports up to 64k queues with 64k entries each.
Intel says the 750 Series achieves peak performance at a queue depth of 128, which is much more than AHCI can muster yet well short of NVMe’s maximum capacity. That’s probably a good place to be at such an early stage in the protocol’s life.
|Capacity||Die config||Max sequential (MB/s)||Max Random (IOps)||Price||$/GB|
|400GB||28 x 16GB||2200||900||430k||230k||$389||$0.97|
|1.2TB||86 x 16GB||2400||1200||440k||290k||$1029||$0.84|
PCIe and NVMe combine to give the 750 Series crushing performance stats for both sequential and random I/O. The flagship 1.2TB config hits 2400MB/s, according to the spec sheet, quadrupling the maximum speed of Serial ATA. Versus last year’s 730 Series, the new hotness is specced for severalfold performance gains on all fronts. You don’t lose too much dropping to the base 400GB model, either.
Although the 750 Series doesn’t match the 2800MB/s sequential peak of Intel’s top datacenter SSD, the DC P3700, it does beat that drive’s random write rating. Credit the firmware, which contains “radical” changes focused on improving random I/O performance. The firmware is also configured to allocate 8-9% of the drive’s total flash capacity to overprovisioned area. That’s similar to the overprovisioning in typical consumer drives but less than the ~25% set aside by the P3700.
Like its enterprise forebear, the 750 Series uses 20-nm NAND fabbed by Intel’s joint flash venture with Micron. The chips weigh in at 16GB apiece, and they’re a lower grade than the top-shelf bin reserved for the P3700. The drive’s endurance rating is much lower as a result, but it’s still more than sufficient for typical consumer usage patterns. The 750 Series is rated to absorb up to 70GB of writes per day over the length of its five-year warranty.
There are no guarantees after the drive’s endurance spec is exceeded, but the 750 Series should be able to write a lot more data before reaching the raw cycling limit of its NAND. (The Intel 335 Series in our SSD Endurance Experiment wrote over 700TB before hitting that media wear threshold.) When the NAND’s limits are reached, the 750 Series is designed to slip into a “logical disable” mode that throttles write speeds severely enough to produce an effective read-only state. Intel’s other consumer SSDs are programmed to brick themselves at the next reboot, preventing users from accessing their data. The 750 Series instead emulates its enterprise counterparts, which remain in read-only mode through subsequent reboots.
Like its server-oriented siblings, the 750 Series comes in two form factors. The half-height, half-length add-in card pictured on the left slots into standard PCIe slots, and Intel throws in a full-height backplate for typical desktop enclosures. The 2.5″ version on the right is meant for traditional drive bays, though its 15-mm thickness requires more headroom than most SSDs.
Both variants use prominent heatsinks to cool the controller and NAND. The 750 Series is rated for peak power draw of 25W, so there’s a lot of heat to dissipate. Thanks to these hunks of finned metal, the drive is rated to withstand ambient temperatures up to 70°C, an important consideration for systems crowded with multiple graphics cards and other high-end components.
Instead of connecting via PCIe slot, the 2.5″ unit has an SFF-8639 jack and associated cabling. Intel ships the drive with an 18″ shielded cable from a company called Amphenol. This cable pipes signaling and clock data for the quad PCIe lanes to a smaller, square-shaped SFF-8643 connector that plugs into the host system. Instead of drawing power from that connection, the cable pulls juice from a standard PSU SATA connector.
The cabled solution purportedly delivers identical performance to the add-in card. It also leaves PCIe slots open for multiple graphics cards, which is why Intel believes the cabled version will end up being more popular than the card.
Intel says the SFF-8643 host connector can be mounted on motherboards in numerous orientations, including an edge-facing config to facilitate clean cable routing. We haven’t seen any motherboards with the requisite SFF jack onboard, though. Asus’ new Sabertooth X99 does come with a compatible connector, but the port lives on a bundled adapter card rather than on the motherboard itself. It may take some time before truly native implementations arrive.
Even with the add-in card, motherboard firmware still needs the right hooks to boot from the 750 Series and other NVMe SSDs. Intel has been working with the major firmware vendors to integrate support for NVMe drives, and UEFI version 2.3.1 has everything that’s required. Motherboard makers have to roll that revision into the firmware for their individual products, of course, but Intel tells us all Z97 and X99 boards should have access to the necessary update. Depending on the firmware, older UEFI-based boards may also work with the 750 Series.
Once you have a compatible motherboard, the next requirement is an operating system with NVMe support. Windows 8.1 has native drivers built in, and Win7 adds them via hotfix. Intel offers its own NVMe drivers, as well, and it claims they’re faster than the ones Microsoft supplies. We used the Intel drivers for all our testing. Speaking of which, let’s dig into the performance analysis on the next page.
To gauge the 750 Series’ performance, we tested the 1.2TB add-in card against three PCIe SSDs: Samsung’s XP941 256GB, Plextor’s M6e, and Intel’s own DC P3700 800GB. The Plextor and Samsung drives have similar per-gig pricing to the 750 Series, but they’re confined to much smaller M.2 gumsticks. They also have slower Gen2 interfaces—two lanes for the M6e and four for the XP941—and AHCI underpinnings.
The P3700 is priced around $3/GB, so it’s obviously in a different league. We’ve included it more for the sake of sibling rivalry than realistic competition. It will be interesting to see how the scaled-back consumer derivative compares.
Recent Serial ATA SSDs from Crucial, Intel, OCZ, and Samsung fill out the rest of the field. That group also includes a SATA 3Gbps drive from the old-timer’s league: Intel’s X25-M 160GB, which was released way back in 2009. The X25-M is marked with a darker shade of gray, while the PCIe SSDs are colored to set them apart from the SATA pack.
IOMeter — Sequential and random performance
IOMeter fuels much of our new storage suite, including our sequential and random I/O tests. These tests are run across the full extent of the drive at two queue depths. The QD1 tests simulate a single thread, while the QD4 results emulate a more demanding desktop workload. (87% of the requests in our old DriveBench 2.0 trace of real-world desktop activity have a queue depth of four or less.) Clicking the buttons below the graphs switches between the different queue depths.
Our sequential tests use a relatively large 128KB block size.
The 750 Series lands in second place throughout our sequential tests, wedged between the faster P3700 and the slower XP941. Although it narrows the gap to the datacenter drive in the four-deep read test, it’s mostly stuck at the mid-point between the two.
That said, the 750 Series hits well over 1200MB/s in the QD1 test, more than doubling the performance of the SATA drives. And it’s even faster at QD4. Regardless of the queue depth, the XP941 is at least 200MB/s behind with reads and 500MB/s behind with writes.
Next, we’ll turn our attention to performance with 4KB random I/O. We’ve reported average response times rather than raw throughput, which we think makes sense in the context of system responsiveness.
Although there’s some intermingling between the PCIe and SATA SSDs, Intel’s NVMe drives continue to occupy the top spots, with the 750 Series trailing the P3700 slightly. Both are consistently ahead of their PCIe competition, and their advantages are especially acute with writes at QD4.
The preceding tests are based on the median of three consecutive three-minute runs. SSDs typically deliver consistent sequential and random read performance over that period, but random write speeds worsen as the drive’s overprovisioned area is consumed by incoming writes. We explore that decline on the next page.
IOMeter — Sustained and scaling I/O rates
Our sustained IOMeter test hammers drives with 4KB random writes for 30 minutes straight. It uses a queue depth of 32, which should result in higher speeds that saturate each drive’s overprovisioned area more quickly. This lengthy—and heavy—workload isn’t indicative of typical PC use, but it provides a sense of how the drives react when they’re pushed to the brink.
We’re reporting IOps rather than response times for these tests. Click the buttons below the graph to switch between SSDs.
Note that there are two sets of results for the 750 Series. The first looks normal, with an initial period of extremely high performance as the drive’s overprovisioned area captures incoming writes. When that area becomes saturated, the write rate plummets, and the march toward a slower steady state begins. Sometimes, though, the 750 Series gets stuck around 200 IOps for the first half of the test. The same thing can happen to the P3700, too. The initial slowdown doesn’t seem to be related to temperature or to the number of IOMeter workers hammering the drive with writes.
Intel recommends pre-conditioning the 750 Series with an hour’s worth of sequential writes immediately before running IOMeter performance tests. But we didn’t pre-condition the competition, so the 750 Series didn’t get any special treatment. Perhaps that explains the anomalous results. In any case, we’re working with Intel to trace the source of the issue. We’ll update this section when we get to the bottom of it.
Apart from the anomaly, the 750 Series looks very strong. It hits nearly the same peak as the P3700, though it doesn’t have enough overprovisioned area to maintain the high for as long. Performance is reasonably consistent after the initial decline, and the IOps even tick up slightly toward the end of the test.
To show the data in a slightly different light, we’ve graphed the peak random write rate and the average, steady-state speed over the last minute of the test.
The 750 Series peaks nearly 2X higher than the next drive down the line, and it’s ahead of the M6e and XP941 by even greater margins. That lead narrows considerably in the final minute of the test, at least versus the top SATA drives. The M6e and XP941 fall to a whopping 5-6X slower than the 750 Series over the long haul, in part because their lower total capacities have less overprovisioned area.
Our final IOMeter test examines performance scaling across a broad range of queue depths. We ramp all the way up to a queue depth of 128. Don’t expect AHCI-based drives to scale past 32, though; that’s the max depth of their native command queues.
We use a database access pattern comprising 66% reads and 33% writes, all of which are random. The test runs after 30 minutes of continuous random writes that put the drives in a simulated used state. Click the buttons below the graph to switch between the different drives. And note that the P3700 plot uses a much larger scale. We’ll compare all the PCIe drives on that scale in a moment.
Were it not for the P3700, I could say that the 750 Series completely dominates the field. “Destroying everything but the datacenter drive” doesn’t quite have the same ring to it.
The 750 Series boasts higher I/O rates right out of the gate, and it continues to ramp up across the full extent of the test. As an added bonus, performance scales particularly quickly at the lower queue depths most indicative of typical desktop workloads.
Somewhat surprisingly, the SATA-based OCZ Vectors come the closest to matching the 750 Series here. The M6e and XP941 have middling I/O rates at best, a point driven home by the graphs below. These plots compare just the PCIe drives on the expanded scale required to capture the P3700’s otherworldly I/O rates. Clickety click to switch between total, read, and write IOps.
At its peak, the P3700 manages about 3X the IOps of the 750 Series. That sounds about right given the similar difference in dollars per gigabyte.
TR RoboBench — Real-world transfers
RoboBench trades synthetic tests with random data for real-world transfers with a range of file types. Developed by our in-house coder, Bruno “morphine” Ferreira, this benchmark relies on the multi-threaded robocopy command build into Windows. We copy files to and from a wicked-fast RAM disk to measure read and write performance. We also cut the RAM disk out of the loop for a copy test that transfers the files to a different location on the SSD.
Robocopy uses eight threads by default, and we’ve also run it with a single thread. Our results are split between two file sets, whose vital statistics are detailed below. The compressibility percentage is based on the size of the file set after it’s been crunched by 7-Zip.
|Number of files||Average file size||Total size||Compressibility|
The media set is made up of large movie files, high-bitrate MP3s, and 18-megapixel RAW and JPG images. There are only a few hundred files in total, and the data set isn’t amenable to compression. The work set comprises loads of TR files, including documents, spreadsheets, and web-optimized images. It also includes a stack of programming-related files associated with our old Mozilla compiling test and the Visual Studio test on the next page. The average file size is measured in kilobytes rather than megabytes, and the files are mostly compressible.
RoboBench’s write and copy tests run after the drives have been put into a simulated used state with 30 minutes of 4KB random writes. The pre-conditioning process is scripted, as is the rest of the test, ensuring that drives have the same amount of time to recover.
Read speeds are up first. Click the buttons below the graphs to switch between one and eight threads.
The 750 Series scores a rare victory over the P3700 in the eight-thread media test, but its advantage is slim, and the two NVMe drives are otherwise closely matched. They have sizable leads over the competition in all but the single-threaded work test, where all the SSDs are tightly bunched.
Samsung’s XP941 is by far the biggest threat overall. It nearly catches the 750 Series in the multi-threaded media test, and it’s clearly the faster of the PCIe alternatives.
Next, we’ll look at write speeds.
Score another win for the 750 Series, this time in the single-threaded work test, where the stakes are admittedly low. The P3700 regains the lead when the thread count increases, and the XP941 almost sneaks into second place. Samsung’s M.2 drive is nowhere near the NVMe duo in the media tests, though. Write speeds are much higher in those tests, and so are the gaps between the 750 Series and its neighbors.
Last, but not least, we’ll see what happens when reads and writes collide in copy tests.
Reading and writing simultaneously produces an exaggerated version of the pattern established in the previous tests. The 750 Series and P3700 have comfortable leads throughout, and their advantages are especially pronounced in the media and eight-thread tests.
Once again, the closest competition is the XP941. Closest doesn’t necessarily mean close, though. The Samsung drive copies media files at almost half the speed of the 750 Series, and it’s over 100MB/s behind in the multithreaded work test.
Thus far, all of our tests have been conducted with the SSDs connected as secondary storage. This next batch uses them as system drives.
We’ll start with boot times measured two ways. The bare test depicts the time between hitting the power button and reaching the Windows desktop, while the loaded test adds the time needed to load four applications—Avidemux, LibreOffice, GIMP, and Visual Studio Express—automatically from the startup folder. Our old boot tests focused just on the time required to load the OS, but these new ones cover the entire process, including drive initialization.
Despite besting most of its competition with ease in our other tests, the 750 Series is by far the slowest to boot the system. It lags more than 10 seconds behind most of the competition in both tests, and it loses even more ground to the M.2 leaders.
We used a slightly different motherboard revision with the NVMe SSDs, but that didn’t slow the P3700 by the same margin, so it doesn’t explain the 750 Series’ sluggishness.
Next, we’ll tackle load times with two sets of tests. The first group focuses on the time required to load larger files in a collection of desktop applications. We open a 790MB 4K video in Avidemux, a 30MB spreadsheet in LibreOffice, and a 523MB image file in GIMP. In the Visual Studio Express test, we open a 159MB project containing source code for the LLVM toolchain. Thanks to Rui Figueira for providing the project code.
None of the SSDs set themselves apart in our first batch of load tests. Maybe the situation will change with games.
Nope. Nothing to see here… except for the six-year-old X25-M G2 matching the load times of the latest SSDs, including Intel’s wicked-fast PCIe drives. Kinda puts things into perspective, doesn’t it?
Test notes and methods
Here’s are the essential details for all the drives we tested:
|Crucial BX100 500GB||SATA 6Gbps||Silicon Motion SM2246EN||16-nm Micron MLC|
|Crucial MX200 500GB||SATA 6Gbps||Marvell 88SS9189||16-nm Micron MLC|
|Intel X25-M G2 160GB||SATA 3Gbps||Intel PC29AS21BA0||34-nm Intel MLC|
|Intel 335 Series 240GB||SATA 6Gbps||SandForce SF-2281||20-nm Intel MLC|
|Intel 730 Series 480GB||SATA 6Gbps||Intel PC29AS21CA0||20-nm Intel MLC|
|Intel 750 Series 1.2TB||PCIe Gen3 x4||Intel CH29AE41AB0||20-nm Intel MLC|
|Intel DC P3700 800GB||PCIe Gen3 x4||Intel CH29AE41AB0||20-nm Intel MLC|
|Plextor M6e 256GB||PCIe Gen2 x2||Marvell 88SS9183||19-nm Toshiba MLC|
|Samsung 850 EV0 250GB||SATA 6Gbps||Samsung MGX||32-layer Samsung TLC|
|Samsung 850 EV0 1TB||SATA 6Gbps||Samsung MEX||32-layer Samsung TLC|
|Samsung 850 Pro 500GB||SATA 6Gbps||Samsung MEX||32-layer Samsung MLC|
|Samsung XP941 256GB||PCIe Gen2 x4||Samsung S4LN053X01||19-nm Samsung MLC|
|Samsung 850 Pro 500GB||SATA 6Gbps||Samsung MEX||32-layer Samsung MLC|
|OCZ Vector 180 240GB||SATA 6Gbps||Indilinx Barefoot 3 M10||A19-nm Toshiba MLC|
|OCZ Vector 180 960GB||SATA 6Gbps||Indilinx Barefoot 3 M10||A19-nm Toshiba MLC|
All the SATA SSDs were connected to the motherboard’s Z97 chipset. The M6e was connected to the Z97 via the motherboard’s M.2 slot, which is how we’d expect most folks to run that drive. Since the XP941 requires more lanes, it was connected to the CPU via a PCIe adapter card. The 750 Series and DC P3700 were hooked up to the CPU via the same full-sized PCIe slot.
If you’ve made it this far, you might enjoy a few more shots of the 750 Series.
We used the following system for testing:
|Processor||Intel Core i5-4690K 3.5GHz|
|Platform hub||Intel Z97|
|Platform drivers||Chipset: 10.0.0.13
|Memory size||16GB (2 DIMMs)|
|Memory type||Adata XPG V3 DDR3 at 1600 MT/s|
|Audio||Realtek ALC1150 with 126.96.36.19944 drivers|
|System drive||Corsair Force LS 240GB with S8FM07.9 firmware|
|Storage||Crucial BX100 500GB with MU01 firmware
Crucial MX200 500GB with MU01 firmware
Intel 335 Series 240GB with 335u firmware
Intel 730 Series 480GB with L2010400 firmware
Intel DC P3700 800GB with 8DV10043 firmware
Intel X25-M G2 160GB with 8820 firmware
Plextor M6e 256GB with 1.04 firmware
OCZ Vector 180 240GB with 1.0 firmware
OCZ Vector 180 960GB with 1.0 firmware
Samsung 850 EVO 250GB with EMT01B6Q firmware
Samsung 850 EVO 1TB with EMT01B6Q firmware
Samsung 850 Pro 500GB with EMXM01B6Q firmware
Samsung XP941 256GB with UXM6501Q firmware
|Power supply||Corsair Professional Series AX650 650W|
|Operating system||Windows 8.1 Pro x64|
Thanks to Asus for providing the systems’ motherboards, Intel for the CPUs, Adata for the memory, and Corsair for the system drives and PSUs. And thanks to the drive makers for supplying the rest of the SSDs.
We used the following versions of our test applications:
- IOMeter 1.1.0 x64
- TR RoboBench 0.2a
- Avidemux 2.6.8 x64
- LibreOffice 4.3.2
- GIMP 2.8.14
- Visual Studio Express 2013
- Batman: Arkham Origins
- Tomb Raider
- Middle Earth: Shadow of Mordor
Some further notes on our test methods:
- To ensure consistent and repeatable results, the SSDs were secure-erased before every component of our test suite. For the IOMeter database, RoboBench write, and RoboBench copy tests, the drives were put in a simulated used state that better exposes long-term performance characteristics. Those tests are all scripted, ensuring an even playing field that gives the drives the same amount of time to recover from the initial used state.
- We run virtually all our tests three times and report the median of the results. Our sustained IOMeter test is run a second time to verify the results of the first test and additional times only if necessary. The sustained test runs for 30 minutes continuously, so it already samples performance over a long period.
- Steps have been taken to ensure the CPU’s power-saving features don’t taint any of our results. All of the CPU’s low-power states have been disabled, effectively pegging the frequency at 3.5GHz. Transitioning between power states can affect the performance of storage benchmarks, especially when dealing with short burst transfers.
The test systems’ Windows desktop was set at 1920×1200 at 60Hz. Most of the tests and methods we employed are publicly available and reproducible. If you have questions about our methods, hit our forums to talk with us about them.
The 750 Series SSD is enterprise trickle-down elevated to a high art. This descendant of Intel’s latest datacenter drives is a rare beast even in PCI Express circles. With a four-lane Gen3 interface backed by the next-gen NVM Express protocol, the 750 Series delivers the future of solid-state storage today.
And oh, what a glorious future it is.
Performance is the real story. The 750 Series may not match Intel’s top server SSD in every workload, but it’s largely in the same ballpark for a third of the price. There’s no contest versus the Samsung XP941 and Plextor M6e, which have slower sequential speeds and much lower random rates. Those drives have a comparable cost per gig, making the 750 Series’ premium pricing entirely justifiable on speed alone.
The keys to such a sweet ride come with some strings attached, though. The biggest challenge is finding desktop tasks that can harness all the horsepower. While the 750 Series delivers incredible performance in targeted benchmarks and demanding sequential transfers, it doesn’t load big files, applications, or games appreciably faster than older SATA SSDs. Storage-bound workloads are required to get the most out of the drive.
There’s also the matter of motherboard compatibility. Although the 750 Series should work in all Z97 and X99 boards, only the latter have enough Gen3 lanes to avoid cannibalizing connectivity to a discrete graphics card. Support for the 2.5″ version’s fancy cable is spotty right now, too. It feels like the 750 Series is a little ahead of its time, and honestly, that’s part of the appeal. One of the best things about co-opting enterprise gear is pushing a system closer to the leading edge.
Another benefit is the additional goodies that tend to come with premium products. The 750 Series’ datacenter origins bestow power-loss protection and blinky diagnostic LEDs, and Intel kicks in a five-year warranty with a high endurance rating. The persistent read-only behavior at the end of the NAND’s life is a comforting bonus, too, as is compatibility with Intel’s excellent Toolbox utility.
As a high-end indulgence, the 750 Series ultimately posts the right numbers, ticks the right boxes, and incites the right emotional responses. It may not provide a palpable improvement for everyday desktop tasks in the same way the first SSDs delivered us from the sluggishness of mechanical drives, but it’s truly next-level storage by every other measure.