I've got an WD Black NVMe drive installed on an older AMD computer with Gen 2 PCIe slots. It's my boot drive and it has reasonable performance but a lot less than I was expecting. I was not paying much attention when I got the generic add in card about two years ago. That card is 4X and I have it plugged into a 16X slot.

I think the 4X card on a Gen2 bus is a bottleneck for the drive? I know that real world performance is probably not significant (I've tested sata SSDs and NVMe drives as boot drive and it's very close), but does anyone know of a 16X card that will work with a NVMe drive? I've seen some on NewEgg but from the reviews it looks like some of them are actually 4x cards even though they have connectors for a 16X slot. That and all of those seem to come from the PRC.

Keeping up with all the changing generations gives me a headache and the thing works and I should probably leave it alone, but I thought I would ask here in case someone knew the scoop.

TIA,

B

A 4x Gen2 pcie connection is a max theoretical bandwidth of 20Gbps, with 20% of that wasted to 8/10b encoding, so on your very best day that will be capable of just under 2000 megabytes per second. Or roughly 2/3 the wd black's rated speed.

M.2 NVME cards are only wired for four lanes, so adding a true NVME 16x adapter will basically just give you the ability to put in four 4x NVME drives, not make the one you have any faster - though two or four drives in an array would get you more speed.

Hey thanks for the reply,

I thought 4x Gen2 was 2Gb/s, is the 20Gbps a typo?

I knew about the overhead and how that would eat up some of the performance but I'm getting 1,660 MB/sec for sequential reads on Crystal Disk Mark.  It's less than half of speed of my other computer with the M.2 slot directly on the motherboard (same drive).

B

You're parsing bits against bytes. 20Gbps = 20 billion bits per second. 20GBps (note capital "B") would imply 20 billion bytes per second. PCIe lanes are generally rated in GHz/bits per second, while disk devices generally get rated in Gibi/Mibi bytes per second.

There has been inconsistent nomenclature, but things seem to have settled down to lowercase "b"ps being bits per second and uppercase "B"ps being bytes per second.

Don't forget gibi versus giga :)

Oh yeah you are correct. I could almost say that they hired politicians to come up with the nomenclature to confuse people. Don't get me started on USB 3 stuff.

Hey thanks for your help.

B

I would suggest getting a current motherboard that supports nvme natively. :p

If you are going to go with a 16x get a card with 4 m.2 headers so you can max it out.

I think asus has a card with 4 ports and active cooling for around $70.