NVMe: Which Form Factor?

[Anna Fire]

Hi, 

Looking to experiment in NVMe  storage specifically for a boot drive and important applications but unsure which form factor to pursue (M.2, U.2 and Add in Card (AiC)). How do their performances differ and what are their trade-offs? Why would I choose one over the other assuming my motherboard supported all of them.

[genexis_x]

I prefer M.2. Small in size, compatible with many motherboards

Performance wise is roughly the same as long as it's NVMe no matter what form factors

 

BTW why you want a NVMe drive? It's expensive

[SCHISCHKA]

disclaimer: i dont have one but i do plan on getting one for my upgrade in a few months. For me it depends on what is available and price. the PCIe form factor is not as cheaply available. Some motherboards place the m.2 slot right underneath the GPU which im not too happy with. I guess it comes down to the motherboard.

[mr moose]

I'm interested in this also, I have seen some M.2 drives labeled as NVMe while still being cheap.  Then there are motherboards where they have the M.2 key but the specs are a little ambiguous. Some read like they are compatible but don;t list the speeds, others suggest they are run only at sata speeds, while others again suggest that they take bandwidth (PCIe lanes) away fro the GPU if using NVMe.

 

Do all motherboards that have the M.2 key support NVMe natively and if so does any M.2 drive that is labeled NVMe run at the full 1500+ speeds?

 

 

 

 

 

[mariushm]

m.2 is a connector that combines up to 4 pci-e v3.0 lanes and sata as fallback (backwards compatibility).

The number of lanes is flexible (sort of), the motherboard manufacturers have the option to wire 2 or 4 lanes to the connector, or they can wire 4 but then disable 2 or even all 4 (if the m.2 drive has sata fallback) in order to re-use those lanes for other things like sata controllers for extra sata ports, or extra usb 3.0 controllers or extra pci-e x1 slots... For example, let user choose in BIOS if they want 4 lanes and disable one or two pci-e x1 slots or use 2 lanes for m.2 and use the other 2 lanes maybe to enable an extra sata controller on a pci-e x1 lane and other things.

 

If the SSD controller can use all 4 lanes, then the SSD can potentially transfer data at up to around 3.9 GB/s in both directions. With 2 lanes, you get around 2GB/s in both directions.

With regular SATA 6gbps, you get around 600 MB/s in both directions.

 

m.2 is cool but a lot of m.2 SSD drives run kinda hot due to having to compact everything in such a small surface (rectangle). Reading reviews for particular drives that interest you would be worth it.

 

Some processors (Ryzen for example) have dedicated pci-e lanes for the M.2 connector, so in that case it would be a shame not to use those pci-e lanes by installing a ssd there. The SATA ports are provided by the chipset which shares a x4 connection to the cpu with other things like usb 3 controllers, pci-e slots , network  etc

 

 

[Anna Fire]

Just now, mr moose said:

I'm interested in this also, I have seen some M.2 drives labeled as NVMe while still being cheap.  Then there are motherboards where they have the M.2 key but the specs are a little ambiguous. Some read like they are compatible but don;t list the speeds, others suggest they are run only at sata speeds, while others again suggest that they take bandwidth (PCIe lanes) away fro the GPU if using NVMe.

 

Do all motherboards that have the M.2 key support NVMe natively and if so does any M.2 drive that is labeled NVMe run at the full 1500+ speeds?

 

 

 

 

 

There are both x4 and SATA M.2 slots. Have to check the motherboard out for which slots are which. The m.2 SATA slots will be bottlenecked to SATA speeds whereas the PCIe x4 NVMe slots use PCIe lanes and are faster. NVMe memory does not take PCIe Lanes away from the GPU. What happens is that the processor dedicates PCIe lanes for both a graphics card and a chip set. The chip set splits up the channels assigned to it into multiple lanes (Although total speeds are limited by the number of dedicated PCIe lanes from the processor) and the NVMe memory use these lanes from the chipset to connect to the system.