Which M.2 slot to use on ASUS Z270E mobo

[saas1980]

I purchased a M.2 SSD to run the OS and my Z270E mobo has x2 M.2 connectors. Does it matter where I plug in the M.2 SSD? The Mobo manual differentiates both available connectors as follow:

M.2_1 socket supports PCIe 3.0 x4 and SATA mode M Key design and type 2242 / 2260 / 2280 / 22110 PCIe and SATA storage devices

M.2_2 socket supports PC 3.0 x4 M Key design and type 2242 / 2260 / 2280 PCIe storage devices

The manual further instructs "Adjust BIOS settings to use SATA device" but does not show how this is done in BIOS. I was under the impression the BIOS would automatically detect the M.2 device. I'm unable to test anything yet as the build is nearing completion but would appreciate if you could shed some light.

 

[USAFRet]

This depends on which specific drive you have.

If it is a SATA m.2 drive, it must go in m.2_1.
Otherwise, either.

But you also have to look in the motherboard user manual to discover what other SATA ports are affected by which m.2 port.

 

[raisonjohn]

Yes, it matters, to a point (depending on the rest of your storage devices to be used).

First, there are two basic types of M.2 SSDs: one is PCIe-based and one is SATA-based.

PCIe-based M.2 SSDs can run in faster speeds, for example, at PCIe3.0 x4 speeds (up to ~32Gbps max.). These PCIe-based M.2 SSDs have either a Key-M, or a Key-B, or a Key B+M. Key-M M.2 SSDs can go up to full x4 speeds, while Key-B and Key B+M can only go up to x2 speeds (~16Gbps in PCIe3.0).

On the other hand, SATA-based M.2 SSDs only run at the same speed as your regular SATA SSD devices (up to ~6Gbps max.). These SATA-based M.2 SSDs can also have the same keying, but, can only reach such relatively slower SATA speeds.

Your motherboard only supports Key-M M.2 SSDs.

The 4-/5-digit numbers in the specs you posted, such as "2242", "2260", "2280", "22110" pertain to the physical length of the M.2 SSD, which doesn't matter much nowadays as most available M.2 SSDs are standard 2280 in length (i.e., "22mm" wide x "80mm" long - hence, "2280").

In your Asus Z270-E motherboard, the M.2_1 slot (the one on the bottom) can support either PCIe-based or SATA-based M.2 Key-M SSDs. The M.2_2 slot (the one on top) can only support PCIe-based M.2 Key-M SSDs (not SATA-based).

When you plug in an M.2 SSD on the top slot (i.e., the M.2_2 slot which only supports PCIe-baed SSDs), it may or may not share lanes with (i.e., disable) two out of your six SATA ports (i.e., the SATA_5 and SATA_6 ports), depending on what speed the M.2_2 slot is configured in your BIOS. If the SSD is running at full x4 speed, it will disable SATA_5 and SATA_6 (you will be left with only 4 SATA ports to use). If the SSD is only running at x2 speed, SATA_5 and SATA_6 can still be used (alongside your 4 SATA ports). To do this go to BIOS:

Advanced Menu > Onboard Devices Configuration > M.2_2 PCIe Bandwidth Configuration > select either [X2] or [X4]​

Now, if you plug in an M.2 SSD on the bottom slot (i.e., the M.2_1 slot), you can also configure this slot to run either in PCIe-mode or SATA-mode. If you set the M.2 SSD to run in PCIe-mode, all of your six SATA ports will be available. If you set the M.2 SSD in SATA-mode, one out of the six SATA ports will be disabled (i.e., SATA_1). This is what is meant by the specs you posted "Adjust BIOS settings to use SATA device" (i.e., pertaining to using a SATA-based M.2 SSD on the Asus Z270-E). To do this, go to BIOS:

Advanced Menu > Onboard Devices Configuration > M.2_1 PCIe Bandwidth Configuration > select either [SATA mode] or [PCIE mode]​

 

[saas1980]

I actually thought all those numbers were model numbers of different types of compatible devices - would never have imagined these related to length.

I believe mines a PCIe device as confirmed on the sellers website https://www.ebuyer.com/766048-samsung-500gb-960-evo-pcie-ssd-mz-v6e500bw

PCpartpicker also confirms the interface as (M) https://uk.pcpartpicker.com/product/Ykbkcf/samsung-960-evo-500gb-m2-2280-solid-state-drive-mz-v6e500.

Hope you can check and confirm.

From what I understand, please correct me if im wrong, I can place my PCIE M.2 SSD on either of the 2 mobo connectors via PCIe-Mode for which both connectors will deliver best performance, difference being which SATA ports being disabled. I went through the manual again and it confirms the above: M.2_1 will disable SATA 1 and M.2_2 will disable SATA 5 and 6. This shouldnt be a problem as I plan on adding only 2 more SATA devices (standard SD + HDD).

I also understand I can check (or change) BIOS to see if M.2_1 is configured correctly to PCIE mode for best performance.

Ideally I might end up choosing the above M.2_2 connector as my GPU somewhat overshadows the M.2_1 at the bottom of the mobo.

 

[saas1980]

I actually thought all those numbers were model numbers of different types of compatible devices - would never have imagined these related to length.

I believe mines a PCIe device as confirmed on the sellers website https://www.ebuyer.com/766048-samsung-500gb-960-evo-pcie-ssd-mz-v6e500bw

PCpartpicker also confirms the interface as (M) https://uk.pcpartpicker.com/product/Ykbkcf/samsung-960-evo-500gb-m2-2280-solid-state-drive-mz-v6e500.

Hope you can check and confirm.

From what I understand, please correct me if im wrong, I can place my PCIE M.2 SSD on either of the 2 mobo connectors via PCIe-Mode for which both connectors will deliver best performance, difference being which SATA ports being disabled. I went through the manual again and it confirms the above: M.2_1 will disable SATA 1 and M.2_2 will disable SATA 5 and 6. This shouldnt be a problem as I plan on adding only 2 more SATA devices (standard SD + HDD).

I also understand I can check (or change) BIOS to see if M.2_1 is configured correctly to PCIE mode for best performance.

Ideally I might end up choosing the above M.2_2 connector as my GPU somewhat overshadows the M.2_1 at the bottom of the mobo.

 

[raisonjohn]

Yes, your M.2 SSD (Samsung 960 EVO) is indeed a PCIe-based device with a Key-M interface.

Both of your Z270-E mobo's M.2 slots are capable of delivering the full PCIe3.0 x4 speeds for your M.2 SSD. With a PCIe-based M.2 SSD in x4 speeds, only the M.2_2 slot (the one on top) will disable SATA ports (SATA 5 and 6). Using your M.2 SSD on the M.2_1 slot (the one at the bottom) in [PCIe-mode] will not disable any SATA ports. The SATA 1 port will only be disabled IF you select [SATA-mode] in BIOS for the M.2_1 slot.

 

[saas1980]

Ah, i gotcha!!

Your first post was clear enough, I don't know how I overlooked the part where you mentioned "If you set the M.2 SSD to run in PCIe-mode, all of your six SATA ports will be available". Well i guess now i'm favouring the M.2 slot at the bottom!

Besides making sure BIOS is set to PCIe-mode for the M.2_1 slot, are there any other settings which i should be attending to before powering up and installing Windows? I have in the past installed OS on both the standard shrouded SSDs and HDDs using a USB stick without any problems (for laptop) - would the same process apply for the PC build or should I check for certain settings first for a smooth run?

 

[raisonjohn]

Yup! You got it.

There are several things/steps that need to be done for you to install OS on the PCIe M.2 SSD and use it as your boot drive. You may want to check these very helpful guides (as they are very detailed):

Guide #1: https://tinkertry.com/how-to-boot-win10-from-samsung-950-pro-nvme-on-superserver
Guide #2: http://forum.asrock.com/forum_posts.asp?TID=1236

 

[Rotem_46]

Hey,
I know its an old thread but it helped me quite a bit today installing my new 500GB Evo 970 Plus on my Asus Z270E Gaming Strix MB.
My previous SSD was the 500GB 850 Evo 2.5" and I wanted to clone it to the new 970 NVMe.
I will write (hopefully in short) what I did as it may help someone else...
OK, so here is what I did: (BTW, all steps were done with 4 additional 3.5" HDD connected! I've read threads where people said all drives must be disconnected)

1. Installed the new drive into the second M.2 slot (M.2_2 which support PCI-E only ) out of the two M.2 the board has.
2. Installed Macrium Reflect Free and cloned the Evo 850 to the Evo 970.
3. Shutdown the PC and removed the 850.
4. Powered up the PC and all was OK only the 970 Evo Plus worked at half speed.
5. Shutdown the PC again, moved the 970 to M.2_1 which support both PCI-E and SATA.
6. Went into the BIOS and under Advanced Menu > Onboard Devices Configuration > M.2_1 PCIe Bandwidth Configuration I chose PCI-e.
7. Powered up the PC again and the drive worked at full speed (3526 read, 3068 write, 295166 random read, 257812 random write).

Also, all of the SATA ports are working so I didn't have to lose any of my HDD's.
I think that's it hopefully it will help someone down the line.

Thanks for the help guys !

* The reason I mentioned the swap between the M.2 slots after the first boot was just to show that it can be done and the OS will still work as it should

My PC:
Asus Z270E Gaming Strix
Intel Core i7 7700K
32GB G.Skill TridentZ 3200Mhz
Asus GTX1070
Evo 970 Plus and 4 x 3.5" HDD
Corsair 620W PSU