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m.2 PCIe vs m.2 SATA

The motherboard I'm using has 2 onboard m.2 slots.

I want to use 2 of the Samsung 960 PRO NVME M.2 SSDs, one that's 512GB for the operating system, and the other is a 2TB for everything else.

What's the difference between hooking one up through PCIe and the other through SATA? Which should be hooked up to PCIe and which should be hooked up through SATA?
Reply to KHendrickson93
11 answers Last reply Best Answer
More about pcie sata
  1. the nvme should go in the pci because the pci is faster

    the other if it is not nvme will do well on the m.2 sata

    the difference is speed, the sata is limited to around 600 megabytes per second, the pcie allows 2000 t0 2500 megabytes per second

    the faster the better

    what motherboard do you have? some will have both m.2 as sata, some with one m.2 sata and the other capable of handling nvme for the pci express speeds mentioned
    Reply to atljsf
  2. atljsf said:
    the nvme should go in the pci because the pci is faster

    the other if it is not nvme will do well on the m.2 sata

    the difference is speed, the sata is limited to around 600 megabytes per second, the pcie allows 2000 t0 2500 megabytes per second

    the faster the better

    what motherboard do you have? some will have both m.2 as sata, some with one m.2 sata and the other capable of handling nvme for the pci express speeds mentioned


    Both m.2s are NVME, so either one would work with the PCIe. The motherboard is MSI X299 GAMING PRO CARBON AC ATX.

    I do not know if both m.2 slots are both PCIe or if one is SATA or not. I can't really find an answer for this. The motherboard specs say:
    "Storage Devices:

    SATA 6Gb/s
    8 x SATA 6Gb/s

    M.2
    2 x M.2 slots (Key M)*
    - Supports up to PCIe 3.0 x4 and SATA 6Gb/s
    - M2_1 slot supports 2242/ 2260 /2280 storage devices
    - M2_2 slot supports 2242/ 2260 /2280/ 22110 storage devices
    - Intel Optane Memory Ready**
    1 x U.2 port *
    - Supports PCIe 3.0 x4 NVMe storage
    * M.2 slots, U.2 port and SATA ports share the same bandwidth"


    I can't tell if that's saying it only has 1 PCIe slot for one of the m.2, and the other has to be a SATA connection?
    Reply to KHendrickson93
  3. Best answer
    KHendrickson93 said:
    Both m.2s are NVME, so either one would work with the PCIe. The motherboard is MSI X299 GAMING PRO CARBON AC ATX.

    I do not know if both m.2 slots are both PCIe or if one is SATA or not. I can't really find an answer for this. The motherboard specs say:
    "Storage Devices:

    SATA 6Gb/s
    8 x SATA 6Gb/s

    M.2
    2 x M.2 slots (Key M)*
    - Supports up to PCIe 3.0 x4 and SATA 6Gb/s
    - M2_1 slot supports 2242/ 2260 /2280 storage devices
    - M2_2 slot supports 2242/ 2260 /2280/ 22110 storage devices
    - Intel Optane Memory Ready**
    1 x U.2 port *
    - Supports PCIe 3.0 x4 NVMe storage
    * M.2 slots, U.2 port and SATA ports share the same bandwidth"


    I can't tell if that's saying it only has 1 PCIe slot for one of the m.2, and the other has to be a SATA connection?


    The MSI X299 Gaming Pro Carbon AC has 2x M.2 sockets both supporting PCIe x4 or SATA speeds. You can use two Samsung 960 Pro NVMe SSD's on those two sockets and both can be configured to run in PCIe x4 speeds.

    If the U2_1 (U.2 connector) is used, and both M.2 SSDs are in PCIe-mode, there will only be 4x SATAIII ports that will be available (SATA1 to SATA4), while the 4x other SATAIII ports (SATA5 to SATA8) will be disabled.

    If the U2_1 (U.2 connector) is not used, and both M.2 SSDs are in PCIe-mode, then, all 8x SATAIII ports (SATA1 to SATA8) will be available.

    Reference: See Page 38 of the motherboard's manual.
    Reply to raisonjohn
  4. raisonjohn said:
    KHendrickson93 said:
    Both m.2s are NVME, so either one would work with the PCIe. The motherboard is MSI X299 GAMING PRO CARBON AC ATX.

    I do not know if both m.2 slots are both PCIe or if one is SATA or not. I can't really find an answer for this. The motherboard specs say:
    "Storage Devices:

    SATA 6Gb/s
    8 x SATA 6Gb/s

    M.2
    2 x M.2 slots (Key M)*
    - Supports up to PCIe 3.0 x4 and SATA 6Gb/s
    - M2_1 slot supports 2242/ 2260 /2280 storage devices
    - M2_2 slot supports 2242/ 2260 /2280/ 22110 storage devices
    - Intel Optane Memory Ready**
    1 x U.2 port *
    - Supports PCIe 3.0 x4 NVMe storage
    * M.2 slots, U.2 port and SATA ports share the same bandwidth"


    I can't tell if that's saying it only has 1 PCIe slot for one of the m.2, and the other has to be a SATA connection?


    The MSI X299 Gaming Pro Carbon AC has 2x M.2 sockets both supporting PCIe x4 or SATA speeds. You can use two Samsung 960 Pro NVMe SSD's on those two sockets and both can be configured to run in PCIe x4 speeds.

    If the U2_1 (U.2 connector) is used, and both M.2 SSDs are in PCIe-mode, there will only be 4x SATAIII ports that will be available (SATA1 to SATA4), while the 4x other SATAIII ports (SATA5 to SATA8) will be disabled.

    If the U2_1 (U.2 connector) is not used, and both M.2 SSDs are in PCIe-mode, then, all 8x SATAIII ports (SATA1 to SATA8) will be available.

    Reference: See Page 38 of the motherboard's manual.


    This comment was very helpful. Does it say if there's any downsides to using both nvme ssds in PCIe x4? Such as bandwidth issues or anything like that?
    Reply to KHendrickson93
  5. No other downsides, except for the sharing of bandwidth among the U.2, M.2, and SATA ports. The PCIe slots (for your GPU and expansion cards) are entirely independent of the lanes of the M.2 socket (which are controlled by your 44-lane, 28-lane, or 16-lane CPU).

    Here are the possible combinations, and its effects, you can do with the U.2, M.2, and SATA ports (highlighted are the combinations you may wish to do when running the two M.2 SSDs in PCIe-mode):

    Combo 1: 1x U.2 + 2x M.2 PCIe + 4x SATA (SATA1, SATA2, SATA3, and SATA4 ports available)
    Combo 2: 1x U.2 + 1x M.2 SATA (upper socket) + 1x M.2 PCIe (lower socket) + 3x SATA (SATA2, 3, & 4 ports)
    Combo 3: 1x U.2 + 1x M.2 PCIe (upper socket) + 1x M.2 SATA (lower socket) + 3x SATA (SATA1, 3, & 4 ports)
    Combo 4: 2x M.2 PCIe + 8x SATA (all SATA ports available)
    Combo 5: 1x M.2 SATA (upper socket) + 1x M.2 PCIe (lower socket) + 7x SATA (all ports avail. except SATA1)
    Combo 6: 1x M.2 PCIe (upper socket) + 1x M.2 SATA (lower socket) + 7x SATA (all ports avail. except SATA2)
    Combo 7: 1x U.2 + 2x M.2 SATA + 2x SATA (SATA3 and SATA4 ports)
    Combo 8: 2x M.2 SATA + 6x SATA (all SATA ports available except SATA1 and SATA2)
    Reply to raisonjohn
  6. raisonjohn said:
    No other downsides, except for the sharing of bandwidth among the U.2, M.2, and SATA ports. The PCIe slots (for your GPU and expansion cards) are entirely independent of the lanes of the M.2 socket (which are controlled by your 44-lane, 28-lane, or 16-lane CPU).

    Here are the possible combinations, and its effects, you can do with the U.2, M.2, and SATA ports (highlighted are the combinations you may wish to do when running the two M.2 SSDs in PCIe-mode):

    Combo 1: 1x U.2 + 2x M.2 PCIe + 4x SATA (SATA1, SATA2, SATA3, and SATA4 ports available)
    Combo 2: 1x U.2 + 1x M.2 SATA (upper socket) + 1x M.2 PCIe (lower socket) + 3x SATA (SATA2, 3, & 4 ports)
    Combo 3: 1x U.2 + 1x M.2 PCIe (upper socket) + 1x M.2 SATA (lower socket) + 3x SATA (SATA1, 3, & 4 ports)
    Combo 4: 2x M.2 PCIe + 8x SATA (all SATA ports available)
    Combo 5: 1x M.2 SATA (upper socket) + 1x M.2 PCIe (lower socket) + 7x SATA (all ports avail. except SATA1)
    Combo 6: 1x M.2 PCIe (upper socket) + 1x M.2 SATA (lower socket) + 7x SATA (all ports avail. except SATA2)
    Combo 7: 1x U.2 + 2x M.2 SATA + 2x SATA (SATA3 and SATA4 ports)
    Combo 8: 2x M.2 SATA + 6x SATA (all SATA ports available except SATA1 and SATA2)


    You lost me with all of those possible combinations. I wouldn't be using the sata ports, and I don't believe I would be using the U.2 port. I only plan to use the two M.2s, both in pcie x4, a single gpu, and a CPU with 28 lanes.

    Out of curiosity, how could I benefit from the U.2? What is its purpose?
    Reply to KHendrickson93
  7. The possible combinations I mentioned pertains to the lane sharing among the U.2, M.2, and SATA ports. Due to such bandwidth sharing of all those ports mentioned, not all of those ports can be used at the same time.

    As you can see in the 8 possible combinations/scenarios of storage devices one might plug in the motherboard, some SATA sockets will be disabled depending on one's specific usage of the U.2 and the M.2 sockets.

    Since you won't be using any of the SATA ports, then, there is no reason to worry which SATA ports will be disabled however you use the U.2 and/or M.2 sockets.

    The U.2 socket is another storage device port (using a different interface than an M.2 or a SATA). For you to use such U.2 socket, you need a U.2 cable such as this: https://www.amazon.co.uk/dp/B01N0O89AW or this: https://www.amazon.com/SFF-8639-Cable-Mainboard-Intel-SFF-8643/dp/B01J3MYD8K . The smaller pin (with 2 male connectors) plug into the U.2 socket of the motherboard. The narrower connector is a SATA power connector that plugs to your PSU's SATA power cable. The wider connector is the U.2 connector that plugs in a U.2 SSD/device such as this: https://www.amazon.co.uk/Intel-SSD-750-800GB-PCIe-x/dp/B013WAZOEG . Using the U.2 socket offers speed of up to PCIe x4 as well. Not much U.2 devices are available though.
    Reply to raisonjohn
  8. raisonjohn said:
    The possible combinations I mentioned pertains to the lane sharing among the U.2, M.2, and SATA ports. Due to such bandwidth sharing of all those ports mentioned, not all of those ports can be used at the same time.

    As you can see in the 8 possible combinations/scenarios of storage devices one might plug in the motherboard, some SATA sockets will be disabled depending on one's specific usage of the U.2 and the M.2 sockets.

    Since you won't be using any of the SATA ports, then, there is no reason to worry which SATA ports will be disabled however you use the U.2 and/or M.2 sockets.

    The U.2 socket is another storage device port (using a different interface than an M.2 or a SATA). For you to use such U.2 socket, you need a U.2 cable such as this: https://www.amazon.co.uk/dp/B01N0O89AW or this: https://www.amazon.com/SFF-8639-Cable-Mainboard-Intel-SFF-8643/dp/B01J3MYD8K . The smaller pin (with 2 male connectors) plug into the U.2 socket of the motherboard. The narrower connector is a SATA power connector that plugs to your PSU's SATA power cable. The wider connector is the U.2 connector that plugs in a U.2 SSD/device such as this: https://www.amazon.co.uk/Intel-SSD-750-800GB-PCIe-x/dp/B013WAZOEG . Using the U.2 socket offers speed of up to PCIe x4 as well. Not much U.2 devices are available though.



    You've been really informative and helpful man. I greatly appreciate the knowledge you've given me today!
    Reply to KHendrickson93
  9. the u.2 as you see, well, i haven't seen a single u.2 device, so is a sort of abandoned technology, m.2 has more future

    some sata ports will be disabled but it has many and you say you will not use any, i would put 1 2 tb hard disk for backup purposes

    unless you have a good backup solution outside the pc it would be unnecessary

    if you have been reading and watching some youtubers, some x299 motherboards have showed problems keeping cool vrm area and is highly recommended to put a fan blowing air over that area, so one of the fans in the back would be good pushing air over that area
    Reply to atljsf
  10. atljsf said:
    the u.2 as you see, well, i haven't seen a single u.2 device, so is a sort of abandoned technology, m.2 has more future

    some sata ports will be disabled but it has many and you say you will not use any, i would put 1 2 tb hard disk for backup purposes

    unless you have a good backup solution outside the pc it would be unnecessary

    if you have been reading and watching some youtubers, some x299 motherboards have showed problems keeping cool vrm area and is highly recommended to put a fan blowing air over that area, so one of the fans in the back would be good pushing air over that area


    I've yet to buy the motherboard. I'm pretty much just waiting till all the kinks and bugs are worked out. I'll give till the end of the year, otherwise, I'm going to pay attention to AMD's threadripper. It will give me time to save up my budget for everything, including the two M.2 nvme ssds.
    Reply to KHendrickson93
  11. raisonjohn said:
    No other downsides, except for the sharing of bandwidth among the U.2, M.2, and SATA ports. The PCIe slots (for your GPU and expansion cards) are entirely independent of the lanes of the M.2 socket (which are controlled by your 44-lane, 28-lane, or 16-lane CPU).

    Here are the possible combinations, and its effects, you can do with the U.2, M.2, and SATA ports (highlighted are the combinations you may wish to do when running the two M.2 SSDs in PCIe-mode):

    Combo 1: 1x U.2 + 2x M.2 PCIe + 4x SATA (SATA1, SATA2, SATA3, and SATA4 ports available)
    Combo 2: 1x U.2 + 1x M.2 SATA (upper socket) + 1x M.2 PCIe (lower socket) + 3x SATA (SATA2, 3, & 4 ports)
    Combo 3: 1x U.2 + 1x M.2 PCIe (upper socket) + 1x M.2 SATA (lower socket) + 3x SATA (SATA1, 3, & 4 ports)
    Combo 4: 2x M.2 PCIe + 8x SATA (all SATA ports available)
    Combo 5: 1x M.2 SATA (upper socket) + 1x M.2 PCIe (lower socket) + 7x SATA (all ports avail. except SATA1)
    Combo 6: 1x M.2 PCIe (upper socket) + 1x M.2 SATA (lower socket) + 7x SATA (all ports avail. except SATA2)
    Combo 7: 1x U.2 + 2x M.2 SATA + 2x SATA (SATA3 and SATA4 ports)
    Combo 8: 2x M.2 SATA + 6x SATA (all SATA ports available except SATA1 and SATA2)


    Hey question for you on this too, I am buying a very similar X299 motherboard, the MSI SLI PLUS, will I be able to achieve the same configurations (and are the M.2 slots on my board going to even support PCIe)? (I will be purchasing the 28 lane CPU, so( x16/x8/x4)... ALSO, would this mean that I can only have an M.2 in x16 mode OR a GPU in x16 mode, or does it not take away from those PCIe lanes? If that were my limitation, what would be the best configuration? I plan to have 1 SATA 1tb HDD, 1M.2 NVMe Samsung 960 Pro, and a High end GPU (no SLI).
    Reply to tybond117
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