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Please explain: M.2 with PCIe vs SATA controller compatiblity

stateofmind

Senior member
Aug 24, 2012
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www.glj.io
Hi and thanks in advance!

I can't figure it out - I have the XPS 9550 laptop with an M.2 SSD. It is a SATA SSD according to HWInfo => It means it uses a SATA controller => M.2 PCIe SSDs will work, but on lower speed

But, some people say it they can run M.2 PCIe SSD on full speed. Could an M.2 connection have two controllers?

Thanks
 

ShintaiDK

Lifer
Apr 22, 2012
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M.2 supports 2 modes. SATA and PCIe. And an SSD only supports 1 mode. So either you got a SATA M.2 SSD or a PCIe.
 

ShintaiDK

Lifer
Apr 22, 2012
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But doesn't it depend on the controller? The M.2 port is connected to both SATA controller and PCIe controller?
Its only connected to one of them. But the slot supports both. If SATA is used, one of the other regular SATA ports will be disabled.
 

stateofmind

Senior member
Aug 24, 2012
245
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www.glj.io
Its only connected to one of them. But the slot supports both. If SATA is used, one of the other regular SATA ports will be disabled.
Thanks, but you are talking about the current connected device
I'm asking if I could connect both, interchangeably.. if it could be that two controllers are used with an M.2 port

I KNOW that the XPS 9550 can house both M.2 SATA and M.2 PCIe NVMe..
 

ShintaiDK

Lifer
Apr 22, 2012
20,395
128
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Sorry I dont follow. You can only have one card in an M.2 slot connected. This can be either SATA or PCIe, not both. And the card will only support 1 type.
 

stateofmind

Senior member
Aug 24, 2012
245
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76
www.glj.io
There are two parts, at least:
1. The M.2 slot/port itself
2. The controller which is the M.2 connected to - SATA/PCIe

In what cases you can use both SATA M.2 and PCIe M.2 SSDs in an M.2 slot? I'm sure it is possible, because it is possible with the XPS 9550
 

ShintaiDK

Lifer
Apr 22, 2012
20,395
128
106
There are two parts, at least:
1. The M.2 slot/port itself
2. The controller which is the M.2 connected to - SATA/PCIe

In what cases you can use both SATA M.2 and PCIe M.2 SSDs in an M.2 slot? I'm sure it is possible, because it is possible with the XPS 9550
Always as such since all slots is pretty much B or M keyed. M.2 requires that both SATA and PCIe is connected to the slot for those. E keyed are too small for SSDs and is for wifi only if there.

In short, if you can plug in an SSD. It supports both types.
 
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stateofmind

Senior member
Aug 24, 2012
245
2
76
www.glj.io
Always as such since all slots is pretty much B or M keyed. M.2 requires that both SATA and PCIe is connected to the slot for those. E keyed are too small for SSDs and is for wifi only if there.

In short, if you can plug in an SSD. It supports both types.
So the keying also means that the appropriate controller is connected?

I truly tried to figure that out from wikipedia and at least 4-5 articles over the web.. how did you find it?

Thanks again!
 

Hellhammer

AnandTech Emeritus
Apr 25, 2011
701
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According to Dell's site, the XPS 15 9550 already has a PCIe SSD. Can you check the hardware ID of the drive and report it, so we can double check the drive and its interface?

Device Manager > Disk drives > Right-click the drive and select "Properties" > Details > Hardware Ids
 

stateofmind

Senior member
Aug 24, 2012
245
2
76
www.glj.io
According to Dell's site, the XPS 15 9550 already has a PCIe SSD. Can you check the hardware ID of the drive and report it, so we can double check the drive and its interface?

Device Manager > Disk drives > Right-click the drive and select "Properties" > Details > Hardware Ids
The name of the SSD is "LITEON CS1-SP32-11 M.2 2242 32GB" and HWInfo says the connection is SATA - I can post the HWInfo file

The bios has three values under "drives" (or something like that) - "SATA 1", "SATA 2" and "M.2 PCIe SSD". I can disable the M.2 PCIe SSD one with no visible effect but not the other two..
 

Hellhammer

AnandTech Emeritus
Apr 25, 2011
701
4
81
The name of the SSD is "LITEON CS1-SP32-11 M.2 2242 32GB" and HWInfo says the connection is SATA - I can post the HWInfo file

The bios has three values under "drives" (or something like that) - "SATA 1", "SATA 2" and "M.2 PCIe SSD". I can disable the M.2 PCIe SSD one with no visible effect but not the other two..
Ahh, so you have the version with hard drive and SSD. In that case, the SSD that's already installed is SATA.

I can't say for sure if PCIe is supported, but given that Dell offers a model with a PCIe SSD it's likely that the non-PCIe SSD version also has PCIe routed to the M.2 slot and the necessary BIOS/UEFI support. The only way to be sure of that is to contact Dell, but from the looks of it, you can replace the SSD with a PCIe one and it should operate at full speed.
 

stateofmind

Senior member
Aug 24, 2012
245
2
76
www.glj.io
Ahh, so you have the version with hard drive and SSD. In that case, the SSD that's already installed is SATA.

I can't say for sure if PCIe is supported, but given that Dell offers a model with a PCIe SSD it's likely that the non-PCIe SSD version also has PCIe routed to the M.2 slot and the necessary BIOS/UEFI support. The only way to be sure of that is to contact Dell, but from the looks of it, you can replace the SSD with a PCIe one and it should operate at full speed.
It is supported because people had success with running the Samsung 950 Pro on the same model

What confused me is that I still don't understand if this is the general case - if the M.2 keying means there is an appropriate controller? Also, the fact that two controllers can be in use with the same M.2 port (maybe chained?)
Quite annoying, because I don't understand how it really works
 

frowertr

Golden Member
Apr 17, 2010
1,371
41
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It is supported because people had success with running the Samsung 950 Pro on the same model

What confused me is that I still don't understand if this is the general case - if the M.2 keying means there is an appropriate controller? Also, the fact that two controllers can be in use with the same M.2 port (maybe chained?)
Quite annoying, because I don't understand how it really works
I'm confused on your question. M.2 is just a connector. It can support PCIe, SATA, and USB bus types depending on the motherboard. If you use it in SATA mode, than typically one SATA port on your motherboard will be disabled to allow that M.2 to be used as a SATA port/bus. You will be limited to SATA 6Gbps in this mode. If you use it in PCIe mode you typically have a choice of AHCI or NVMe. Four PCIe lanes are exposed to the M.2 in PCIe mode no matter if it's AHCI or NVMe. Of course your SSD has to support NVMe to use that as a logical interface and I also believe the motherboard must support NVMe as well. AHCI drives are much more common currently. Four lanes at PCIe 3.0 means you get a max theoretical throughput of 32Gbps.

At least this is how I understand everything to work. Please someone correct me if I'm wrong.
 
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stateofmind

Senior member
Aug 24, 2012
245
2
76
www.glj.io
I'm confused on your question. M.2 is just a connector. It can support PCIe, SATA, and USB bus types depending on the motherboard. If you use it in SATA mode, than typically one SATA port on your motherboard will be disabled to allow that M.2 to be used as a SATA port/bus. You will be limited to SATA 6Gbps in this mode. If you use it in PCIe mode you typically have a choice of AHCI or NVMe. Four PCIe lanes are exposed to the M.2 in PCIe mode no matter if it's AHCI or NVMe. Of course your SSD has to support NVMe to use that as a logical interface and I also believe the motherboard must support NVMe as well. AHCI drives are much more common currently. Four lanes at PCIe 3.0 means you get a max theoretical throughput of 32Gbps.

At least this is how I understand everything to work. Please someone correct me if I'm wrong.
But are you sure it works like that?
What confused me is that I see no confirmation it works like you did (or don't understand) - why are you sure that both the SATA and PCIe controllers can be used? that both are connected? in which case? always?
Also, some articles said that if you can use a PCIe NVMe SSD, then you probably can't use a SATA SSD in the same slot, because of the controller
 

frowertr

Golden Member
Apr 17, 2010
1,371
41
91
Also, some articles said that if you can use a PCIe NVMe SSD, then you probably can't use a SATA SSD in the same slot, because of the controller
The keying of the device will dictate what bus is exposed. Look at the connector difference between a M.2 PCIe x4 NVMe (or non-NVMe) SSD and a M.2 SATA SSD. You will notice the that the PCIe x4 device only has one notch while the SATA device has two. Those extra pins that are exposed in the M.2 connector for the x4 device are the PCIe lanes. That's what makes the device use 4 lanes of the PCIe bus.

I know for a fact you can use a SATA M.2 drive in a M.2 port that supports PCIe/NVMe as that is what I'm currently doing with a Gigabyte Z170N Gaming 5 Motherboard. I'm running a M.2 Samsung 850 EVO which is only SATA and my motherboard supports NVMe/PCIe.

If you want to know without a doubt if you can use the PCIe 3.0 x4 NVMe bus for your current SSD take it out and look at it. If it only has one notch then it's M keyed and can be used as a x4 PCIe device.

If it has two notches it's B keyed and can either use PCIe x2 (AHCI) or SATA depending on the SSD. Obviously you can't use the PCIe bus if your drive is SATA only. I'm betting it's SATA only.
 
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