Question Why is my M.2 SSD Card slower than my Internal SATA SSD

Spiderkeys

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I brought a m.2 for the first time, a green WD m.2 card.

I'm benching marketing it with CrystalDiskMark, and why it it losing to the SATA drive

M.2 is about 460MS/s

SATA SSD gets about 560MS/s

This disappoints me, I brought a M.2 because I heard they were faster.

My OS is installed and running on my M2, would that be giving me false results?
 
M.2 is a form factor, it has nothing to do with actual speed. The WD Green still operates using SATA lanes so it will be limited to SATA speeds.

M.2 NVMe SSDs on teh other hand use PCIe lanes so there speeds is much much faster.

However even that is dependent on what you are actually doing because Random read/write speeds is negligible and the speed advantage of a PCIe speed NVMe drive really only shows in sequential reads/writes.
 

Spiderkeys

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Oh I see, my WD GREEN M.2 2280 240GB Card is obviously not a NVMe, just found out it says on the box up to 545MS/s, yet I only get around 460MS/s on benchmarks.

Hmm, I'm starting to think I just made a mistake by cloning my OS to the M2 and erasing the internal SATA SDD. But still I notice no difference. :|
 
Oh I see, my WD GREEN M.2 2280 240GB Card is obviously not a NVMe, just found out it says on the box up to 545MS/s, yet I only get around 460MS/s on benchmarks.

Hmm, I'm starting to think I just made a mistake by cloning my OS to the M2 and erasing the internal SATA SDD. But still I notice no difference. :|
I believe the WD Green are DRAM less which means although most are still faster then HDDs (Some DRAM SSDs are slower) they will not be as fast as other SSDs that do have DRAM Cache.
 

Maxxify

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M.2 is a form factor that allows for both the PCIe and SATA interfaces (and both NVMe and AHCI protocols). When using a SATA drive the port acts like a logical SATA port, that is to say it's effectively the same as a physical SATA port/drive.
 
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Maxxify

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There's nothing virtual about it afaik, the M2 port has physical dedicated wiring for Sata and the PCH just switches the connections from the normal Sata ports to the M2
I meant it in reference to being logical: "The M.2 specification provides up to four PCI Express lanes and one logical SATA 3.0 (6 Gbit/s) port, and exposes them through the same connector." Semantics though, physically it does go the same place; I'll edit for clarity.
 
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Maxxify

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Oh ok. no problem, I thought maybe there was more indepth that I wasn't aware of.
Well, primary M.2 sockets on AMD boards use direct CPU lanes and you can put a M.2 SATA drive into one of those and obviously does not switch from normal SATA ports. In fact, I can use any one of my three M.2 sockets (X570 Aorus Master) without conflicting with any SATA ports. Where there's a switch is between the 2nd chipset M.2 socket with a PCIe drive (NVMe or AHCI) and one block of SATA ports (2 ports on my board, but up to 4 per block). So it's a bandwidth/lane issue.

Additionally, while SATAe and M.2 have the same connectivity, SATAe has two physical SATA ports while the M.2 spec is for a single logical SATA port. So physically different, obviously, because SATA is both a connector and a bus interface; obviously there are pins that can be remapped with an adapter though. So by "virtual" I meant that it's effectively a SATA drive from the system's perspective even if it uses a different interface, may not take a port, and may not even go over PCH. "Logical" is the correct and accurate term, I used "virtual" for the user's understanding but I shouldn't do that in this case.
 
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