ASUS Prime Z270-A - Which M.2 Slot?

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Jay5435

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Feb 7, 2014
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I'm just ordered a Samsung 960 Evo to add to my Asus Prime Z270-A motherboard, It has two M.2 slots, i'm just wondering if there is an performance advantage in use the M.2_1 vs M.2_2

Thanks.
 
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Well according to the site

*1. The M.2_1 socket shares SATA_1 port when use M.2 SATA mode device. Adjust BIOS settings to use a SATA device.

*2. The M.2_2 socket shares SATA_56 ports when use M.2 PCIE mode device in X4 mode. Adjust BIOS settings to use M.2 PCIE devices
 
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I don't think there is at the moment, unless someone else shows a graft proving that.
I was looking at the mobo specs so you might not see much of a difference at all.
https://www.pugetsystems.com/labs/articles/Overview-of-M-2-SSDs-586/
I think reading this will help explain things much more better, but as it stands your new samsung will be the best it can be in M 2.1 mode.
 
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Which M2 slot doesn't require changing the BIOS and disabling a SATA port when using a NVMe SSD in PCIE x4 mode?
 
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I installed my 960 Evo NVMe drive on M.2_1 slot,set it to PCIE only and it did not seem to disable any SATA ports. At least its not disabled in the BIOS. I have not actually plugged my DVD-ROM into every SATA port to test though.
 
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Also I saw a post where it said that the M.2 drives performance will slow down when they get hot, so putting it in the M.2_1 slot should help keep it cooler.
 
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I don't think that will help anything at all, unless your computer case has a specific fan on the front or sides to cool it,
It'll still act the same just like a normal sata hdd's when they get warmed up while working hard.
 
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I was looking for this answer too. I currently have a question in to ASUS about it but they haven't gotten back to me yet. I have my M2 in the M.2_1 slot now. For this slot you can purchase a 3D printed attachment that will hold a fan over the drive to help keep it cool, so this is the ideal slot. the other slot is under the graphics card... I just want to make sure the M.2_1 slot is using X4 bandwidth by default, I don't care if SATA slots get disabled cause I only have one DVD drive. In the BIOS the setting to change from X2 to X4 is only for the M.2_2 slot.
 
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I talked with ASUS support today and they told me the M.2_1 slot runs at X4. Therefore to me, this is the ideal slot, due to the distance from normal graphics card location, the fact that you can get the M2 fan holder for slot 1, and you don't lose any SATA slots. To use the 2 slot, you have to change the BIOS setting to get the best perforamnce and lose 2 SATA slots and have your drive under your graphics card
 
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I have a Samsung 960 pro coming from NewEgg tomorrow........wondering about which m.2 slot to put it in my Asus Prime z270-ar? and what bios changes I have to make?
 
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Use the M.2_1 slot running in PCIE mode. If you plan on transferring lots of data at a time, I'd recommend getting the 3D printed fan holder and 40mm fan. I've read that it will start to throttle after about 45-60 seconds of transferring data due to heat.

 
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Just an update. I have the Samsung 960 Evo in the M.2_1 slot. I also have 2 Samsung 850 Evo SSD's. When attached to the SATA_1 port, the 850 Evo would only transfer at 200MBs. I had to switch that one to SATA_5 to get full 500MBs from the 850 Evo.
So maybe it is only half speed on SATA_1 when M.2_1 is used in PCIE? Any idea if a BIOS setting change can enable full speed on SATA_1 without effecting the 960 Evo on M.2_1?
 
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check the manual - the M.2 slot that supports SATA mode shares the bandwidth with some SATA port - I think port 1 (the one that gets disabled if m.2 used in SATA mode).
So if it was my computer, I'd connect SATA SSD to the port that is not shared with M.2 port.
 
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ASUS states:
*1. The M.2_1 socket shares SATA_1 port when use M.2 SATA mode device. Adjust BIOS settings to use a SATA device.

It's unclear, but from the way it is written, it sounds like it should only effect SATA_1 port when the M.2_1 slot is used in SATA mode. Since I am using M.2_1 in PCIe mode, SATA_1 should not be effected?
 
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From the BIOS part of the manual (Section 3.6.8). SO to me this also reads as, if you use a PCIe device in M.2_1 slot, then the SATA1 port should work fine.


SATA mode Configuration: [SATA_12][M.2_1]

[Auto] Auto-detects the M.2 device mode. If a SATA device is detected,

SATA6G_1 will be disabled.

[SATA mode] Only supports M.2 SATA devices. Please note that SATA6G_1 port cannot

be used in this mode.

[PCIE mode] Only supports M.2 PCIE devices.
 
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My primary concern is the speed and the ssd cooling. I have the STRIX Z270F with one M.2 PCIe SSD. So, which is the better port for me?

M.2_2:
- closer to the CPU (less latency?)
- closer to the CPU cooler: I have a huge cooler with 2 fans, so having that installed I won't be able to remove my SSD. On the other hand this may help forcing some airflow around.
- it is just above the video card, so the vertical airflow is blocked.
- does not block SATA port: not a concern to me

M.2_1:
- the only heat source close on the board is the chip with a heat sink above. Heat source above should not be a concern.
- ariflow can go around the SSD in both horizontal and vertical direction, practically none of them blocked.
- this one is closer to the front case fan, however closer to the bottom front mounted HDDs. I could install a second case fan in the front, but not yet decided about it.
- blocks 2 SATA port from the 6: as I have only 3 SATA devices, still one remains for later use
- easier access: I have already ordered an Alphacool HDX that I would like to install later. In this port it would be easy, in the 2. port I would not be able to do that without removing the CPU cooler.

I am thinking about testing both scenarios with an infrared thermo meter I have access to. Having that done I will let you know the result.


 
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Assuming the M.2 slots in the Z270F are similar to the Z270-AR, the M.2_1 slot seems to be the best for NVMe M.2 SSD for a number of reasons.

1) M.2_1 in PCIE mode is not supposed to share any SATA slots (M.2_2 in X4 mode (required for full speed of the 960 Evo) disables SATA 5 & 6)
2) It is lower in the case, away from heat sources so should be cooler. M.2_2 sits between GPU and CPU, both generate a lot of heat.
3) You can add a M.2 printed fan holder and 40mm fan (highly recommended)


I bought a second Samsung 960 Evo so am now using both M.2 slots. I have a 40mm fan on the M.2_1 slot.
I tested transferring 100GB of video from one drive to another and back. Initial write speeds for both where around 2GBs. After about 25-30 seconds the one with the fan (M.2_1) slowed to about 1.2GBs and stayed steady. The one without the fan slowed to about 560MBs with 10 seconds or less. To the touch the one without the fan was noticably hotter and got hot pretty quick (like just a few seconds of writing). The one with the fan warmed up fairly quick too but was only warm, not hot.

Without a fan, these drives can heat up quick and throttle when transfering lots of data. I highly recommend getting the fan holder and a good fan. Also of note, is that when throttled, the speeds are only 10% better than the Samsung 850 Evo SSD (reads and writes at around 500MBs) which is a lot cheaper.

Here is an article on the Samsung NVMe SSD heat throttling issues.
https://www.pugetsystems.com/labs/articles/Samsung-950-Pro-M-2-Additional-Cooling-Testing-795/

 
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Hi,

i got a Samsung SSD 960 Evo 500gb and also got the Z270F Mainboard.


i unplug all sata devices insteed dvd-drive at sata 3 and i put the ssd in m.2_1 (the one at the bottom).

When i start the PC to install windows 10 64 bit home via dvd, it doesnt work, do i need to change something at the bios? i heard something about setting the ssd to uefi mode or something like that, someone got a idea? :)

sorry for my bad english
 
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See the links here:
https://rog.asus.com/articles/guides/m-2-ssd-windows-install-guide/
 
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