ASRock Z97 Extreme6 Review: Ultra M.2 x4 Tested With XP941
by Ian Cutress on May 24, 2014 12:00 PM ESTAs part of our review, ASRock sent us the 512 GB Samsung XP941 M.2 drive to test how ASRock has implemented the feature. For more information on the drive, check out Kristian’s review here. Kristian, due to his Z87 setup, had to use an M.2 x4 to PCIe adapter card, whereas with the Z97 Extreme6 we can test it direct.
On the Z97 motherboards we have seen so far, they have all implemented an M.2 x2 slot, with the two lanes coming from the eight PCIe 2.0 lanes possible off of the Z97 chipset. These slots are often also SATA capable, and share bandwidth with other SATA ports, a PCIe 2.0 x4 slot or the SATA Express implementation. The Z97 Extreme6 does this with its own M.2 x2 slot, but it has the Ultra M.2 x4 slot that comes direct from the CPU.
The Haswell CPUs for the Z97 platform have 16 lanes of PCIe 3.0 which are split into two lots of eight. One of these eight can be split into two lots of four, and it is typical to see on a motherboard a multi-GPU arrangement of x8/x4/x4 from the CPU. It is these last four lanes that ASRock has adapted for its M.2 slot, which means that when an M.2 drive is placed into the x4 slot, it will reduce the bandwidth of the first two PCIe slots down to x8/x4. This also disables SLI, due to NVIDIA’s requirement for x8 PCIe lane allocation (either PCIe 2.0 or 3.0) for each graphics card.
We tested the XP941 in both the x4 and x2 slots to find the general performance values of the drive when restricted by the x2 or given full reign of the x4. Because the x4 is rated at PCIe 3.0, ASRock is claiming a peak bandwidth of 32 Gbps, or 4 GBps, for drives attached. This would be a significant increase over the standard state of SATA storage, which tops out at 600MBps in real world implementations over a 6 Gbps connection. That would also imply that the 32 Gbps from the x4 should give 3.2 GBps as an upper limit.
We ran a series of tests with the XP941 in the M.2 x4, both while the integrated graphics was enabled and a discrete GPU (dGPU) in the first PCIe slot, and the M.2.
| ASRock Z97 Extreme6 M.2 Performance | ||||||
| M.2 x4 | M.2 x4 w/dGPU | M.2 x2 | ||||
| Read | Write | Read | Write | Read | Write | |
| AS SSD | 1095 | 918 | 1095 | 942 | 765 | 647 |
| ATTO QD4 | 1015 | 1074 | 1028 | 1081 | 679 | 827 |
| ATTO QD10 | 1013 | 1074 | 1020 | 1079 | 687 | 829 |
| IOMeter | 1347 | 1347 | 828 | |||
| HDTach | 1047 | 905 | 607 | |||
Using the drive in the M.2 x4 slot, with or without a discrete GPU in place, gives peak readings about the same, although with the discrete GPU in place ATTO shows some improvement in small transfer sizes (+30% at 4KB with QD10).
However the upshift from x2 to x4 shows the effect of a drive restricted against a drive that can stretch its legs. We move up from 765 MBps read to 1095 MBps read in AS SSD, a 43% speed up. We are still a way away from the 32 Gbps suggested by ASRock that this slot can handle, but it does mean the headroom is there for faster devices.
Moving on to the effect of losing lanes on discrete GPU gaming, we took the system with the M.2 equipped and tried our benchmarks on a single HD7970 (comparing x16 to x8) and two HD7970s in CrossFire (comparing x8/x8 to x8/x4).
| Effect on Average FPS on PCIe 3.0 x16 to x8 | |||
| PCIe 3.0 x16 | PCIe 3.0 x8 | Difference | |
| F1 2013 | 127.6 | 127.5 | -0.1% |
| Bioshock Infinite | 71.0 | 71.4 | 0.6% |
| Tomb Raider | 44.6 | 44.4 | -0.4% |
| Sleeping Dogs | 48.3 | 48.1 | -0.4% |
| Company of Heroes 2 | 42.9 | 42.3 | -1.4% |
On single GPU gaming, at our 1080p Maximum settings presets, gave almost zero difference with the bandwidth difference. The biggest drop was 1.4% for Company of Heroes 2. If this is the worst effect of dropping down from PCIe 3.0 x16 to x8, then I am encouraging all manufacturers, especially those making mini-ITX motherboards, to seriously consider ways to implement a M.2 x4 slot on their products.
This also has an effect on laptop computing, especially those with integrated discrete graphics cards. It means that the laptop manufacturer can implement either one or two M.2 x4 drives in a notebook and still have eight lanes for the GPU which will not be adversely affected in frame rates.
Now on to two-way CrossFire:
| Effect on Average FPS on PCIe 3.0 x8/x8 to x8/x4 | |||
| PCIe 3.0 x16 | PCIe 3.0 x8 | Difference | |
| F1 2013 | 117.5 | 113.6 | -3.3% |
| Bioshock Infinite | 133.3 | 131.8 | -1.2% |
| Tomb Raider | 87.2 | 88.0 | 0.9% |
| Sleeping Dogs | 94.1 | 93.7 | -0.4% |
| Company of Heroes 2 | 42.4 | 42.3 | -0.3% |
Here we see a bigger drop of 3.3% with F1 2013, and the bandwidth drop might affect us more if we had bigger screens at our disposal or a multi-monitor setup. But even 3.3% is not that bad, moving frame rates from 117.5 to 113.6 FPS is an arguable change at best.
All this points to one of several outcomes:
- NVIDIA release their x8 lane restriction for PCIe 3.0 so users can implement SLI with M.2 x4
- Intel increases the lanes on their mainstream CPUs to 20, giving x8/x8 allocation on PCIe and four lanes configurable M.2/SATAe
- Nothing happens, because the performance on one GPU is not badly affected.
I will be hoping for a combination of the first two, just because it would open up more possibilities in this world of desktop computing.
OS Installation
A topic that has arisen on forums since the launch is whether the M.2 drives can be used as boot drives. For UEFI installation, the detection algorithm in the firmware has to be active to see the drive at the install prompt, however for Legacy installation the drive needs to implement its own firmware at POST. As the XP941 does not have initialization drivers, my Legacy Windows 7 install that I normally do for reviews, while it saw the drive at the OS installation screen, it was unable to hook the drive in to install. This is for both the M.2 x2 and M.2 x4 slots on the ASRock motherboard. Placing the drive into an ASUS motherboard showed no drive at all for Legacy installation, however Kristian has been in contact and confirmed that they are working on enabling UEFI installation for M.2 in a future BIOS update, as should all the manufacturers be if they have not already.
When the motherboard manufacturers have updated UEFIs, the following table should be relevant:
| Legacy OS Intall | UEFI OS Install | |
|
M.2 without M.2 POST Firmware (e.g. Samsung XP941) |
No | Yes |
|
M.2 with M.2 POST Firmware (e.g. Plextor M6e) |
Yes | Yes |
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peterfares - Saturday, May 24, 2014 - link
It was stated in the article, using 4 lanes for M.2 from the chipset would leave too little lanes left for controllers and other onboard peripheral devices.SirKnobsworth - Sunday, May 25, 2014 - link
The chipset allows up to 8 PCIe lanes. Maybe having 8 USB 3 ports and 10 SATA ports matters for some, but certainly not everyone. If you use 4 lanes for M.2 you can still have 4 additional lanes going to the NIC/x1 slots/whatever, 4 USB 3.0 ports, and 6 SATA ports, noting that FlexIO allows some flexibility in that arrangement.Galatian - Sunday, May 25, 2014 - link
This! Thousand times this! I mean at least give the option. My PC if only a gaming machine. I have one SSD inside, one mouse, one keyboard and one XBox Controller receiver. I have no need for more ports. At least give me some option: as I said it's either this extreme or the other extreme, but nothing in between.isa - Sunday, May 25, 2014 - link
But the article also said a reason was m.2 cards would mostly or only be offered in 2 channel flavors, and that makes no sense to me since I believe the z97 chipset supports 4 channels of PCIe 2.0 for m.2. I agree many would want 4 channels even if meant sacrificing a few usb ports or whatever, so I'd think the market would provide 4 channel m.2 cards to support those customers.Luke_Higdon - Sunday, April 10, 2016 - link
Question: "Can you explain to me why no mainboard manufacturer is using 4 lanes from the chipsets PCIe 2.0? I mean that would be enough for the Samsung SSD and still has room left."Answer: No It would run at a third the speed.
Question: I mean what do I gain from all those SATA and USB ports? Who is actually using all of them?
Answer: Lots of people including me. I have 6 hard drives a CD player. Plus they are very cheap to make so if you buy an upgraded motherboard this is the least they could do. I understand most people don't need all of that but that is why you would buy a cheaper Motherboard. However most people have 2 hard drives and a DVD player and it is used for adapters and if you are doing RAID it could need double the amount of SATA ports or triple.
Statement: Right now I have to choose between either a slow M.2 slot because they only allocate 2 lanes or I can go with ASRock which feels like overkill and takes away CPU PCIe lanes.
Answer: ASrock doesn't take away PCIe lanes. CPU's are given a fixed amount of PCIe lanes typically 16. If you have a video card it takes 8 and you are left with 8 in which 4 are taken from the 950 pro. If you dont play video games and use integrated graphics from a motherboard then you can buy any motherboard that uses 3.0 PCIe for at least one slot which is most of them.
Marlowe - Saturday, May 24, 2014 - link
All new motherboards should have pcie x4 m.2 slots to be worthwile.. There are really no excuse not to. The x2 version is a too small upgrade from old SATA. Anyone who buys a new fast pcie ssd will need x4 to fully utilize it.I think you can install both Win 7 and Win 8 in UEFI mode.
SirKnobsworth - Sunday, May 25, 2014 - link
A few thoughts:- The SSD only supports PCIe 2.0, not 3.0, so the maximum theoretical bandwidth is 20 rather than 32 gbps. The actual performance is still far below that too though. To my knowledge there are not PCIe SSDs currently available that support gen 3, though I think OCZ will be shipping 2.0x8 SSDs soon.
- Leaked roadmaps show that Intel will be increasing the number of PCIe lanes on the chipset rather than the processor - the chipsets accompanying Skylake should have 20 PCIe 3.0 lanes. If you want more lanes directly from the CPU then there's already an option - Intel's LGA2011 Enthusiast options have 40 PCIe 3.0 lanes from the CPU.
ShieTar - Monday, May 26, 2014 - link
Also, if the x2 port maxes out at 765 MBps of just below 6 Gbps, than we probably should not expect more than roughly 12 Gbps from the x4 port either. So the XP941 would be significantly closer to the interface maximum than the article suggests.Laststop311 - Thursday, May 29, 2014 - link
A lot of people want to build mini itx form factor. LGA 2011 doesn;t exist and never will it's physically too large a socket. All the people like me have a great need for increased pci-e lanes from the cpu. Controllers degrade performance and add latency.At the same time for mini itx you can only fit one pci-e slot on there but it would be nice if we could keep it at 16x for when gpu's do start needing the extra bandwidth and still have 8x left over for 2 4x m2 slots. 24x pci-e 3.0 cpu lanes needs to be on their mainstream. That still leaves a whole 16x gap to the enthusiast and they can increase those by 8 too to 48 lanes and keep the separation the same. Then everyone can be happy.
romrunning - Thursday, May 29, 2014 - link
I will add my vote to wanting a mini-ITX board. To me, I really don't know anyone who is actually using 3 PCIe slots. However, I do know quite a few who are tired of the big towers.Also, where are these people who want a ton of SATA slots in a home PC?? The only chassis I know where I want that many ports is in a server, and there I'm getting space for 16-24 drives - not this Frankenstein of 10 SATA slots. People at home who need a lot of space (for work or pleasure) are getting a NAS, not trying to load out a machine with 6-10 drives.
My picture of a great mini-ITX board - Z or H 9-series chipset, 4 x 6Gbps SATA ports supporting RAID 0/1/5/6, 2 x m.2 (x4) supporting RAID 0/1, no SATA Express (waste of space), 1x eSATA, 4-6 USB 3.0 ports, optional mSATA/PCIe slot for wireless add-on, and a single x16 PCIe 3.0 slot. Price it at $110-150, and I'd buy it in a heartbeat!