Question SATA vs PCI 2.0 x16 PCI 3.0 x4 bandwidth confusion

[maddogmcgee]

Hi

I need to buy a new hard drive. I would prefer a m.2 NVME drive but only have one slot in my b450 tomahawk. Should have gone the x570. RIP.

The drive will roughly be mid tier in performance.

Currently thinking of getting an expansion card and maybe stealing my wife's motherboard next upgrade (it has an extra nvme slot). I will use the 1, 4 and 5 slots.

The slot it is going in is a PCIe express 2.0 x16 slot so I should get 8 Gb/s vs the 6Gb/s of a SATA drive?

Orico M.2 NVMe to PCIe 3.0 X16 Expansion Card - Umart.com.au

Buy Orico M.2 NVMe to PCIe 3.0 X16 Expansion Card - Buy Now, Pay Later + FREE pick-up & same day dispatch!

www.umart.com.au

My second question is, my board supports m.2 PCIe 3.0 x4.... so a maximum link speed of 4Gb/s. Being slower than the SATA connection does not seem right to me? What am I missing? Is this an issue of looking at link speed when I should be looking an bandwidth throughput?

Thanks in advance

 

[RLGL]

Do your research not all boards will accept an M.2 mounted on an expansion card.

 

[Insert_Nickname]

The slot it is going in is a PCIe express 2.0 x16 slot so I should get 8 Gb/s vs the 6Gb/s of a SATA drive?

Actually, you'll get 1000MB/s from the slot. Bandwidth for a single PCIe 2.0 lane is 500MB/s compared to a SATA3's 6Gbit (750MB/s). So a x2 connection yields 1000MB/s.

Somewhat illogically, when moving to PCIe 3.0 a lane does not "double up" as PCIe 1.0 vs 2.0 but "only" jumps to 985MB/s. You still get almost double the bandwidth, but the speed is a bit lower due to using a different encoding scheme.

My second question is, my board supports m.2 PCIe 3.0 x4.... so a maximum link speed of 4Gb/s. Being slower than the SATA connection does not seem right to me? What am I missing? Is this an issue of looking at link speed when I should be looking an bandwidth throughput?

A PCIe 3.0 x4 connection is 32Gbit. Which works out at 4000MB/s. So there is plenty of bandwidth compared to SATA there.

 

[damian101]

Do your research not all boards will accept an M.2 mounted on an expansion card.

I'm pretty sure that all do, PCIe is PCIe. Older boards often can't boot from Nvme drives, but that's a different story.

 

[maddogmcgee]

Thanks for the explanations. I knew I was going wrong. Seems like even the PCIe 2.0 will be fine for my needs, at least in the interim.

 

[RLGL]

I'm pretty sure that all do, PCIe is PCIe

NO, there are several Asrock boards that I have seen in the Asrock forums that Will NOT "see" an M.2 on a PCIe add on card.

 

[Insert_Nickname]

NO, there are several Asrock boards that I have seen in the Asrock forums that Will NOT "see" an M.2 on a PCIe add on card.

This goes for pretty much all boards. But just because you can't see the drive in the BIOS/UEFI doesn't mean it won't work. The OS (installer) will still see it just fine, and will boot from it no problem.