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A 1400 MB/s SSD: ASRock's Z97 Extreme6 And Samsung's XP941
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1. High-Performance Storage On ASRock's Z97 Extreme6

When the Advanced Host Controller Interface was standardized a decade ago, it was built around mechanical storage. In truth, it did an admirable job replacing the moribund IDE standard that preceded it. And even as SSDs came into their own, this programming interface to SATA was still good enough. At least at first.

Today, it’s holding SSDs back. Solid-state storage doesn’t need to exist in the same form factors as mechanical storage, nor does it need the same kind of programming interface. Intel's Z97 Express platform controller hub, which Thomas covered for the first time in Intel Z97 Express: Five Enthusiast Motherboards, $120 To $160, gives us the newest example of enabling SSDs in many shapes and sizes. It takes us away from a vestigial SATA/AHCI ecosystem to a new place where PCIe and SATA Express create an even clearer distinction between mechanical and solid-state storage.

As you start seeing more M.2 PCIe- and SATA Express-equipped boards, think future-ready. Neither plug will do you a ton of good initially. But they pave the way for a new world of storage on the desktop and in mobile applications. You get SATA ports for legacy devices, and the newer interfaces for the latest SSDs. At some point in the future, we'll get to a place where we can forgo AHCI altogether, and instead reap the benefits of solid-state storage through AHCI’s replacement, NVMe.

Meet ASRock's Z97 Extreme6

Serving as our spirit guide through this uncharted landscape is ASRock’s Z97 Extreme6. Thomas wasn't particularly bowled over by Z97's evolutionary changes. But I couldn't help but wonder whether the chipset enables storage nirvana (there isn't much to differentiate Z97 from Z87, after all).

The Z97 Extreme6 is one of ASRock's higher-end models with support for multi-GPU configurations, premium audio, and overclocking. But my interests in it are specific to the platform's storage capabilities.

The board exposes 10 SATA 6Gb/s ports. Six are native to Intel's Z97 Express PCH, while four attach to a pair of ASMedia ASM1061 controllers. One port connects to an eSATA interface on the rear panel, also.

That SATA Express connector is shared with two SATA ports and the M.2 socket. As you'll see, Intel's drive to push innovation in the storage space on mainstream core logic causes some of the same traffic jams we're accustomed to describing on the graphics side (shared PCI Express lanes and all of that).

Surprisingly, perhaps, even though SATA Express is brand new, that's not the big feature here. Rather, it's the Ultra M.2 x4 socket. Wired not through the PCH (like the standard M.2 interface on Z97's ports 13 and 14, along with SATA Express), it isn't subject to the same limitations. It instead utilizes four lanes of PCI Express 3.0 siphoned off of the CPU, yielding up to 32 Gb/s of bandwidth. And while you'll never get 4 GB/s out of it, the right SSD could make for a special evening of benchmarking. 

And wouldn't you know it? We have Samsung's XP941, an OEM-oriented drive, for testing. It uses four PCI Express lanes and comes equipped with the hardware to match. That'll allow us to determine if Intel's Z97 Express and ASRock's Z97 Extreme6 come together to make storage dreams come true.

2. M.2 And SATA Express, Discussed

M.2 PCIe

Intel ratchets up the utility and flexibility of Z97 in a small but profound way. This is achieved by making the chipset’s port 13 and 14 far more flexible than they were in the past. Previously, those two ports facilitated two of the PCH's six SATA interfaces. Now they're flexible, accommodating two big pieces of storage infrastructure: SATA Express and M.2 PCIe.

M.2 PCIe isn’t anything new. As far back as September of last year we were covering that in SanDisk A110 PCIe SSD: Armed With The New M.2 Edge Connector. More recently, we posted Plextor M6e 256 GB PCI Express SSD Review: M.2 For Your Desktop, testing the M.2 PCIe-based SSD on a half-length, half-height add-in board. We were told Plextor was also planning a version without the adapter, which suggested that there'd be motherboards with the corresponding two-lane slots. That day should be today. But as boards equipped with M.2 PCIe slots start selling, SSDs able to drop into them are few and far between.

It's actually pretty easy to mix up M.2 for PCIe and SATA. We're facing the same sort of confusion experienced when mSATA surfaced for mini-PCIe slots. Except this time, it's ever harder to distinguish between M.2 storage with SATA controllers and M.2 PCIe SSDs. So let's just forget about the SATA-based drives and focus on storage natively designed to drop onto the PCI Express bus through the M.2 form factor.

This form factor is flexible in that it can be molded into a wide range of single- or double-sided PCBs. An M.2 device is 22 mm wide, easily fitting a processor and NAND flash packages. Build a longer PCB and you get more space to add flash. Considering Samsung can cram its 1 TB 840 EVO mSATA into roughly the same space as a M.2 2260 (60 mm-long) form factor, something like a M.2 22110 (110 mm-long) gives you a ton of space to work with. And as manufacturing advances, increasing density, it's hard to imagine a day when M.2 will limit the upper bound of capacity.

M.2 Real Estate (in mm)42 mm (M.2 2242)

60 mm (M.2 2260)

80 mm (M.2 2280)
110 mm (M.2 22110)
Single-Sided

924 mm2

1320 mm21760 mm22420 mm2
Double-Sided1848 mm22640 mm23520 mm24840 mm2

Most M.2 PCIe SSDs will utilize two PCI Express lanes (in the case of Z97 Express, of course that means second-gen transfer rates). But Samsung's XP941 is unique in that it communicates over four. That makes it the most ideal candidate for testing ASRock's Z97 Extreme6 and its four-lane PCI Express 30 Ultra M.2 socket.

SATA Express

SATA Express replaces SATA 6Gb/s. The Serial ATA International Organization realized that doubling SATA's transfer rate again wasn't going to be practical. As Paul Wassenberg of Marvell fame told me last year at Flash Memory Summit 2013, SATA Express makes a lot more sense.

As the working group scaled up SSDs from one to eight PCIe lanes in testing, power consumption went through the roof as lanes were attached. But with just two lanes at third-gen transfer rates, power didn’t increase much compared to a SATA 6Gb/s-connected equivalent drive, even as performance was vastly superior. We know from the challenges presented by 12 Gb/s SAS that a cost-effective implementation would be difficult to achieve for SATA. Meanwhile, SATA Express wouldn't be as problematic. Given its PCI Express roots, however, cabling was the challenge to address.

Unlike M.2 PCIe SSDs, which can span up to four lanes, SATA Express uses just two. But whereas a M.2 PCIe-based drive is basically stuck to the motherboard, SATA Express employs cables to make more remote connections, just like SATA. This poses a few practical issues. An external PCIe-based SSD needs a signal from the clock generator. Carrying that signal over distance requires shielding and a beefier (more expensive) cable. So, to combat a prohibitively pricey implementation, the signal can be provided by the solid-state device itself.

Gain a Port, Lose a Port

Based on Intel's implementation of SATA Express in Z97, if you utilize the new technology, you lose access to two of the storage controller's SATA 6Gb/s ports and the M.2 interface. If you instead choose to go with M.2 (the devices are more plentiful, after all), you can't use SATA Express.

To help add a bit of clarity, I created the flow chart above to clarify M.2 PCIe and SATA Express, along with the AHCI and NVMe interface specifications.

On Z97, the PCH-provided M.2 and SATA Express ports are mutually exclusive. You cannot use both simultaneously. Asus is adding third-party SATA Express controllers to some boards, so obviously those are able to operate independently. And then there's ASRock's solution: borrowing four lanes from the CPU's PCI Express controller to create the Ultra M.2 slot. Let's look at that in more depth...

3. Z97 Express: The Same Old Bandwidth Limitations

Not surprisingly, bandwidth through the Z97 Express platform controller hub to the host processor is limited by Intel's DMI interface, based on PCI Express 2.0. That connection won't be updated to third-gen transfer rates until Skylake, which is still two generations away. But Intel's mainstream desktop chipset doesn't just need the bandwidth advantages of PCIe 3.0, it could also really benefit from more lanes than the eight it offers currently.

We know this because we've already looked at how multi-drive SSD arrays on Intel's 6 Gb/s ports are cut off at the knees. Last year, with a stack of SSD DC 3500s and ASRock's C226 WS motherboard, I put together Six SSD DC S3500 Drives And Intel's RST: Performance In RAID, Tested, and the ceiling was made quite clear. Z87 Express offered six 6 Gb/s ports of connectivity, but three decent SSDs are enough to saturate the DMI's limited bandwidth. Sixteen-hundred megabytes per second was basically the limit.

Does any of that change in Z97 Express? How does the addition of SATA Express and a second-gen x2 slot sharing the same limited throughput alter the equation?

Of course, as we've established, ASRock's Z97 Extreme6 is unique. It does have a two-lane M.2 PCI Express 2.0 slot competing for the PCH's limited bandwidth. But it also employs what ASRock calls Ultra M.2, which is a second slot tapping into a Haswell-based CPU's 16 lanes of third-gen PCIe, too. This slot isn't affected by the chipset. And if you drop a PCIe M.2 drive into the Ultra slot, you can still use SATA Express, which is wired into Z97. In exchange, you can't run a graphics card using the processor's 16 lanes, instead bumping it down to eight. Perhaps more severely, SLI and CrossFire configurations are out, too.

But I'm a storage guy. Giving up complex graphics arrays is alright in my book.

So, here's a breakdown of the DMI bandwidth problem. With four SATA 6Gb/s drives in RAID 0, we're limited to around 1600 MB/s. When you factor in the PCH-attached M.2 slot, available bandwidth doesn't change. But the distribution does. Finally, we add Samsung's XP941 in ASRock's special Ultra slot. It doesn't cannibalize Z97's throughput, but as we apply a workload to every device simultaneously, check out how much bandwidth we can push through the Samsung compared to Plextor's M6 and four-drive array of SSD DC S3500s.

Each device gets a workload of 128 KB sequential data with Iometer 2010. We start with the four-drive RAID 0 array, which are already limited by the DMI interconnect. As expected, we see roughly 1600 MB/s. Then, we add the two-lane M.2 slot hosting Plextor's M6e, a PCIe-based drive. The read task is simultaneously applied to it and the RAID 0 configuration.

Not surprisingly, total bandwidth still adds up to ~1600 MB/s. But it's split unevenly between the M.2 slot and SATA 6Gb/s ports. No matter what combination of storage you use attached to Z97 Express, there's a finite ceiling in place. I concede that most desktop users won't ever see the upper bounds of what DMI 2.0 can do. But it's worth noting that Intel arms this chipset with more I/O options than the core logic can handle gracefully. 

Then we add Samsung's XP941, which does its business free of the DMI's limitations. It alone delivers as much throughput as Intel's four SSD DC S3500s. That's notable because, when you think about it, a single SSD in the PCH-attached M.2 slot monopolizes as much as half of the DMI's available headroom. As storage gets faster and the DMI doesn't, an increasing number of bottlenecks surface.

The same workload pushing writes (rather than reads) demonstrates even lower peak throughput, topping out north of 1300 MB/s. We saw the same thing last year in our Z87 Express-based RAID 0 story.

Tapping into the CPU's PCIe controller with a four-lane M.2 slot dangles a tantalizing option in front of storage enthusiasts like myself, eager to circumvent the Z97 chipset's limited capabilities. I understand that most enthusiasts, even the most affluent power users, won't have six SSDs hanging off of their motherboards. But it really doesn't take much to hit the upper bound of what a PCH can do. And DMI bandwidth is shared with USB and networking too, so we're even assuming those subsystems are sitting idle.

This is what the Disk Management console looks like with four SSDs on Intel's 6 Gb/s ports, Plextor's M6e in the PCH-attached M.2 slot, the USB 3.0 Windows to Go storage device used to boot the OS, and Samsung's XP941. Only the last device isn't sharing throughput through Intel's DMI.

Think you might try working around these issues by dropping a four- or eight-lane HBA onto your motherboard? Wrong. Remember, unless you're tapping into the processor's third-gen PCIe lanes, all expansion goes through Z97 Express, subjecting you to the same limitations. Professionals who need more should simply look to one of Intel's higher-end LGA 2011-based platforms. 

I remain critical of PCIe-attached storage without NVMe (the time for that is coming). However, AHCI doesn't stop Samsung's X941 from demonstrating sexy performance characteristics. And ASRock's Z97 Extreme6 is really the only board able to expose its potential right now. Let's take a closer look and suss out the extent of its advantage in the Ultra M.2 slot.

4. Testing Samsung's XP941 On Z97 Express

In most of the stories we write, it doesn't matter where Windows is installed. Storage testing is a bit different though, particularly when we need to turn off the PCH's SATA ports. Thus, utilizing Windows to Go makes a lot of sense. A fully-functioning image can be ported from one machine to another over USB 3.0. It's just as quick as an installation to a SATA-attached SSD, and it enables testing methodologies otherwise considered impractical.

Note also that we're using Intel's new Rapid Storage Technology 13-series driver. It doesn't have much bearing on today's story; the fancier features will get rolled into a version of the RST software later this year. But it was time to upgrade, and so I have.

Test Hardware
ProcessorIntel Core i5-4670K (Haswell), 22 nm, 3.3 GHz, LGA 1150, 6 MB Shared L3, Turbo Boost Enabled
MotherboardASRock Z97 Extreme6
MemoryG.Skill Ripjaws 8 GB (2 x 4 GB) DDR3-1866 @ DDR3-1333, 1.5 V
System Drive Muskin Ventura Ultra 240 GB USB 3.0 UASP
Drive(s) Under TestSamsung MZHPU512HCGL-00000 512 GB M.2 Gen 2 x4 PCIe, AHCI
Power Supply
Seasonic X400 FL2, 80+ Platinum
ChassisLian Li A01-NB ATX
HSF
Noctua NH-L9i
Graphics
Intel HD Graphics 4600
OS
Windows 8.1 Enterprise, Windows to Go
Drivers
STORAHCI.SYS (Generic AHCI), Intel RST 13.1 (SATA)
Comparison DrivesPlextor M6e 256 GB M.2 PCIe x2, Firmware: 1.00

Plextor M6S 256 GB SATA 6 Gb/s, Firmware: 1.00

Plextor M6M 256 GB mSATA 6 Gb/s, Firmware: 1.00

Adata SP920 256 GB SATA 6 Gb/s, Firmware: MU01

Crucial M550 512 GB SATA 6Gb/s, Firmware: MU01

Intel SSD 730 480 GB SATA 6 Gb/s, Firmware: L2010400

SanDisk X210 512 GB, Firmware X210400

Crucial M500 240 GB SATA 6Gb/s, Firmware: MU02

Samsung 840 EVO 250 GB SATA 6Gb/s, Firmware: EXT0AB0Q

Samsung 840 Pro 256 GB SATA 6Gb/s, Firmware DXM04B0Q

Seagate 600 SSD 240 GB SATA 6Gb/s, Firmware: B660

OCZ Vector 256 GB SATA 6Gb/s, Firmware: 2.0

Plextor M5 Pro 256 GB SATA 6Gb/s Firmware: 1.02
Benchmarks
ULINK DriveMaster 2012
DM2012 v980, JEDEC 218A-based TRIM Test, Protocol Test Suite
Test Specific Hardware
SAS/SATA Power Hub, DevSlp Platform, PCIe SSD Power Adapter
Tom's Hardware Storage Bench v1.0
Intel iPeak Storage Toolkit 5.2.1, Tom's Storage Bench 1.0 Trace Recording
Iometer 1.1.0# Workers = 1, 4 KB Random: LBA=16 GB, varying QDs, 128 KB Sequential, 16 GB LBA Precondition, Exponential QD Scaling
PCMark 8
PCMark 8 2.0.228, Storage Consistency Test
5. Results: A PCIe SSD's Sequential Performance

Samsung's 512 GB XP941 is the first four-lane PCI Express M.2 drive in our lab, and we want to know how it performs. In order to figure out what the SSD is capable of, we'll mix up some of the tests from our other storage reviews. First, we benchmark it in ASRock's Ultra slot, which won't limit the device's peak throughput. Then we compare those results to the PCH-attached M.2 slot, which I expect will artificially cap its potential. 

Sequential reads and writes are most likely to illustrate my point, so we start there.

Sequential Reads

If you read the previous page, then you won't be surprised by an outcome of 1250 MiB/s in the M.2 slot attached to our Haswell-based Core i5-4670K. A conversion to decimal lands us right around 1.4 GB/s.

Swap the drive over to a PCH-attached M.2 slot, though, and the binary read throughput drops precipitously. Eight-hundred megabytes per second is nothing to sneeze at. But that's still 33% less than the result measured from ASRock's Ultra slot.

Now check out Samsung's otherwise well-reviewed 840 Pro. It looks shabby in comparison, even though we know it to be one of the best SATA 6Gb/s options available. Then again, there's more to the performance story than just sequential throughput.

Sequential Writes

Sequential writes are even more illustrative of the puissant ASRock Z97 Extreme6/Samsung XP941 combo.

And here's why. The 840 Pro gives us almost 450 MB/s of peak bandwidth (again, in binary). Samsung's XP941 in the PCH-attached, two-lane M.2 slot offers a substantial increase, appearing just under 800 MB/s. The SSD should be commended; it can fully exploit a pair of PCI Express lanes, which SanDisk's A110 and Plextor's M6e cannot do.

Then the XP941 jumps up a notch by peaking in excess of 1000 MB/s when we drop it onto ASRock's CPU-attached Ultra M.2 four-lane slot. That's basically what two of the fastest 6 Gb/s SATA drives achieve in RAID 0.

6. Results: A PCIe SSD's Random Performance

Random performance is another issue entirely. We already know that throughput ceilings aren't as much of a concern when it comes to moving around lots of small chunks of data. In fact SATA 6Gb/s is typically sufficient for heavy random workloads. 

The Samsung XP941 employs AHCI, which has some inherent overhead that chokes the potential of solid-state storage. NVMe was designed to address this. However, Intel's NVMe driver isn't expected until the end of 2014. As a result, we have to accept that a PCIe-based SSD utilizing AHCI is probably going to demonstrate modest advantages, at best. How does the XP941 stack up in the two different connectors exposed by ASRock's Z97 Extreme6?

Random Read Performance

Given what we saw on the previous page, it'd be easy to assume that Samsung's XP941 is capable of massive transactional performance working with small random transfers. The truth is a matter of relativity.

Yes, 120,000 IOPS is an impressive result. But that number doesn't reflect the potential of Samsung's hardware the same way sequential transfers do. And yes, the four-lane Ultra M.2 slot does yield better results. However, the scaling isn't there to indicate that a two-lane interface attached to the PCH was really hamstrung, either.

Even more telling, the two- and four-lane interfaces track alongside the SATA 6Gb/s-based 840 Pro up until a queue depth of 16. Desktop workloads typically don't see that much concurrency, so the XP941 wouldn't confer much benefit.

Random Write Performance

This is mostly what I would have expected based on our previous work with PCIe-based SSDs utilizing AHCI. The SATA-attached 840 Pro takes top honors, even if it isn't the fastest SSD around. Samsung's XP941 falls flat connected to the two-lane M.2 slot. It fares better when we hook up with the four-lane Ultra M.2 interface, though not in any way that'd lead us to favor such a configuration over familiar SATA. 

Bottom line: the random performance of a PCIe-based SSD is more pedestrian than the impressive sequential scores, largely due to AHCI. Still, if you stopped here and didn't look at any other benchmark, you might conclude that Samsung's XP941 is the greatest desktop-oriented SSD ever. But our testing in Iometer isn't necessarily indicative of how the drive behaves in the real world. We need to go into more depth.

7. Results: Tom's Hardware Storage Bench v.1.0

Most of the Z97 Express-based boards you see will include the chipset's six SATA 6Gb/s ports. Some will also feature the PCH-attached M.2 slot we're testing today. And others will expose SATA Express. The Z97 Extreme6's most prominent differentiator is that x4 M.2 slot wired into Intel's LGA 1150 interface, though.

We aren't testing SATA Express yet, and that's for good reason. Most of the first drives will be AHCI-based. And that means they won't be much different from SSDs like SanDisk's A110, which we've already reviewed. As you look at the benchmark results for Samsung's XP941 on a two-lane M.2 interface, consider that a stand-in for SATA Express. The story only really gets interesting once NVMe support is added.

Storage Bench v1.0 (Background Info)

Our Storage Bench incorporates all of the I/O from a trace recorded over two weeks. The process of replaying this sequence to capture performance gives us a bunch of numbers that aren't really intuitive at first glance. Most idle time gets expunged, leaving only the time that each benchmarked drive is actually busy working on host commands. So, by taking the ratio of that busy time and the the amount of data exchanged during the trace, we arrive at an average data rate (in MB/s) metric we can use to compare drives.

It's not quite a perfect system. The original trace captures the TRIM command in transit, but since the trace is played on a drive without a file system, TRIM wouldn't work even if it were sent during the trace replay (which, sadly, it isn't). Still, trace testing is a great way to capture periods of actual storage activity, a great companion to synthetic testing like Iometer.

Average Data Rate

The Storage Bench trace generates more than 140 GB worth of writes during testing. Obviously, this tends to penalize drives smaller than 180 GB and reward those with more than 256 GB of capacity.

In this abbreviated performance analysis, we cut out a lot of the SATA 6Gb/s drives you're used to seeing in our charts. The results are generated under Windows 8.1, whereas our library of data is mostly based on Windows 7. We had some issues using the Ultra M.2 slot under that older operating system, though. Previously, Windows 7 used MSAHCI.SYS. Windows 8 uses the STORAHCI.SYS driver for PCIe-based SSDs. We found the newer driver serves up less consistent latency and service times, dramatically affecting storage performance. Meanwhile, Samsung's 840 Pro is controlled by Intel's RST driver, so it doesn't care either way. For reference, we explored the implications of both drivers in Plextor M6e 256 GB PCI Express SSD Review: M.2 For Your Desktop.

Samsung's XP941 in ASRock's unique Ultra M.2 slot posts the highest average data rate, followed by the same SSD in a PCH-attached M.2 slot. The SATA 6Gb/s 840 Pro takes third place, managing to lead SanDisk's A110, which also connects to the PCI Express bus. Plextor's M6e finishes in last place.

But service times are also important in a test like this one.

Service Time

This is a plot of read and write service times. Reads are on the x-axis; write service times are on the y-axis. These numbers are far more important than average data rates on their one. And using both metrics, we can make far more precise observations about drive performance with real workloads.

As always, down and left is where you want to be. Numbers closer to the origin indicate better performance.

Don't compare these results to any of our previous reviews. Again, they were generated under Windows 8.1, which is less kind to PCIe-attached solid-state storage due to a reliance on the operating system's STORAHCI driver. I'm expecting the picture to change quite a bit once NVMe hits the scene. But for now, Windows 8 lets us put these AHCI-based drives on equal footing.

And Samsung's XP941 shows that it's not held back by STORAHCI. The drive outmaneuvers the other PCIe-based data points in write service times, so long as it's attached to ASRock's Ultra M.2 slot. Going through Intel's Z97 chipset, regardless of whether you're talking about SATA 6Gb/s or M.2, results in a similar outcome.

8. Results: PCMark 8 Storage Consistency Test

PCMark 8's Storage Consistency test is fast becoming my favorite canned benchmark. Usually, that's code for lazy benchmarking. But the folks at Futuremark really came up with something stellar using PCMark 8's real-world workloads. What we end up with are trace-based tests played back to back, with specific conditioning that happens prior to each round. I've gone into a lot of depth on this in past reviews, so if you'd like to know more, I invite you to go back and read the background page.

PCMark 8 Storage Consistency Test: Bandwidth

PCMark 8's Adobe Photoshop (Heavy) trace is far and away the most intensive of the trace bundle. That's why we use it to show latency and bandwidth data for each of the 18 constituent rounds.

I'll let you guess which line on the graph represents Samsung's XP941.

Have you figured it out yet? Here's a hint: it's the fastest one. And not by a small amount, either. The XP941 serves up a benchmark-setting 700 MB/s in the recovery rounds. It dips as low as 500 MB/s in the debilitating degrade phase, which is simply unheard of. Even attached to the Z97 PCH's two-lane M.2 slot, it's still intensely quick. There's just a less capable interface supporting it.

Samsung's XP941 is as much as 20x faster than some of the quickest 6 Gb/s SSDs in this particular trace from this particular benchmark (that is to say our results don't necessarily map over to other workloads). It's hard to overlook the crushing defeat Plextor's M6e (in purple) and Samsung's own 840 EVO (in orange) sustain at the hands of this M.2 drive.

Despite my skepticism of AHCI-based PCIe storage, Samsung at least shows its XP941 to be an exception to the rule.

And here are the overall scores, showing the best and worst scores across PCMark 8's 18 rounds. No surprise, Samsung's XP941 owns the top tier. ASRock's Ultra M.2 slot hosting Samsung M.2 drive pushes as high as 5016 PCMarks. Attached to the PCH's M.2 interface, it registers a score of 4999.

9. ASRock's Z97 Extreme6: Only Satisfied By Samsung's XP941

If you're into storage like I'm into storage, ASRock's Z97 Extreme6 is something special. On one board, it exposes SATA, two-lane M.2 attached to the platform controller hub (at second-gen signaling rates), SATA Express, and four-lane M.2 wired straight into the CPU (at third-gen signaling rates).

Of course, compromises abound, mostly imposed by Intel's chipset. Using the Ultra M.2 slot means borrowing PCI Express connectivity from your graphics card, pulling it into x8 mode. That doesn't leave enough lanes for multi-card arrays. Then again, dropping drives onto Z97 can be tricky, too. The M.2 and SATA Express interfaces share ports with SATA, cutting you to four available 6 Gb/s interfaces if you utilize either interface. 

Will most of our readers need to worry about overpopulating the PCH? No. Do enthusiasts typically push more than 1600 MB/s of data through their mainstream motherboards? No. But if anyone needs to know about the limitations of Z97 Express, it's you, the Tom's Hardware reader.

Our First Four-Lane M.2 SSD

Samsung's XP941 SSD is nice, to start. It's not perfect; that'd take NVMe support. But Samsung isn't to blame for the ecosystem not being ready yet. NVMe won't make it into Intel's driver until the Rapid Storage Technology 3.7 release, slated for introduction at the end of 2014. For now, then, we have AHCI, which leeches away some of the goodness the XP941 could have otherwise enabled. You can still flog this thing and generate insane sequential transfer rates exceeding what two SATA 6Gb/s could do in RAID 0.

Still, the XP941 only makes sense in one special place: thin, light, and expensive laptops. In that application, it cannot be matched. Practically, though, you're going to have a hard time justifying the purchase. And that's assuming you can buy/use it at all. Samsung's XP941 shows up on Amazon from a couple of smaller vendors, marked up substantially. Because it's an OEM product lacking option ROM information, you'll also have a hard time using it as a boot drive on many platforms. Really, unless you're buying ASRock's Z97 Extreme6 for a desktop build, the XP941 is little more than a footnote at this point.

Although I do appreciate the technology exploration, the real revolution in storage is going to happen later, as NVMe rises to prominence and we get SATA Express-attached drives. As we get closer to Intel's Skylake introduction, two generations down the road, more emphasis will be placed on increasing SSD performance as platform controller hubs are equipped with PCIe 3.0 signaling. 

During the course of my testing with the Z97 Extreme6, I used a number of different M.2-based SSDs. ASRock's layout is clever in that its storage sockets lay horizontally between PCIe slots. In this way, installed drives never conflict with GPUs or RAID cards mechanically. The company's special Ultra M.2 interface is only useful if vendors create drives able to utilize it. Surely there is some interest in incredibly fast storage, and what is currently a feature on one board from one manufacturer could balloon into something of a cult hit. Remember, X99 is coming soon, and Haswell-E is going to have PCIe connectivity to spare. Might we see Ultra M.2 resurface on an ASRock board?

Hopefully. PCIe-based SSDs have been around for years. And although they first surfaced as inelegant SATA-based devices attached to HBAs, we're now looking at very small solutions natively designed to communicate across the PCI Express bus. The obscene price premiums that previously kept PCIe storage out of enthusiast desktops is diminished. And to match the XP941's performance, you'd need much more expensive enterprise-oriented drives. 

That's why it's worth considering an M.2 PCIe SSD for your next storage upgrade. ASRock gets credit for innovating on its Z97 Extreme6, embracing the one product out there able to exploit a four-lane link and building a board that takes four lanes from the CPU to enable screaming sequential throughput, without tripping over the DMI's limited bandwidth. It's just too bad that the ecosystem and market are so far apart on the concept right now. It'll be much easier to make the case once NVMe (as an interface), SATA Express, and M.2 (as form factors) gain some traction early in 2015. By then, we'll hopefully be seeing more motherboards able to exploit the capabilities of super-speed SSDs.