# PCIe NVMe Gen3 vs Gen4



## LFaWolf (Sep 12, 2019)

Hi, I have not kept up with the NVMe or SSD tech. Does having a Gen4 NVMe SSD in a Gen3 slot will limit the performance of the Gen4 SSD? If so, by how much? I know Gen4 doubles the bandwidth, but does not only affect sequential read/write and not random read/write?


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## Mussels (Sep 12, 2019)

it halves the maximum bandwidth

how much it slows a drive will vary, but it will slow reads and writes to within the limits of the slot its placed in


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## LFaWolf (Sep 12, 2019)

The drive that I am interested in - https://www.newegg.com/corsair-force-mp600-2-tb/p/N82E16820236549?reviews=all
My question is, will I achieve the rated speed or close to the rate speed, by putting it in a Gen3 NVMe slot? 

This is a Gen3 drive and the rated speed is not half of the Corsair drive. Am I misunderstanding the spec?
https://www.newegg.com/seagate-firecuda-510-2tb/p/N82E16820248080?Item=N82E16820248080


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## Mussels (Sep 12, 2019)

the gen 3 4x slots can do around 4GB/s (3.5GB/s seems to be closer to reality)
gen 4 4x slots can do around 8GB/s, but no drives max it out yet


halving the bandwidth to the slot doesnt mean the drives run at half speed


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## LFaWolf (Sep 12, 2019)

Thank you, that is exactly the info I am seeking. Seems like with the Corsair drive I can max out the bandwidth.


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## TheLostSwede (Sep 12, 2019)

LFaWolf said:


> Thank you, that is exactly the info I am seeking. Seems like with the Corsair drive I can max out the bandwidth.


Maybe, but only in sequential data transfers.
I would avoid the first generation of PCIe 4.0, as they rely on a modified PCIe 3.0 controller with a faster bus and no other enhancements. They also run quite hot.


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## The Egg (Sep 12, 2019)

Correct, it only caps the maximum bandwidth of the SSD, assuming the drive is capable of exceeding PCIe 3.0 x4 speeds in the first place.  It shouldn't have any effect on random I/O.

In fact, on a couple occasions I've used inexpensive PCIe adapter cards to run M.2 drives on older PCIe 2.0 motherboards which didn't have native M.2 slots, and still saw significant improvement over the early 120GB SATA SSDs they were running.   The vast majority of the benefit is coming in at below even PCIe 2.0 (or PCIe 3.0 x2) bandwidth.


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## lamonz88 (Dec 28, 2019)

LFaWolf said:


> Thank you, that is exactly the info I am seeking. Seems like with the Corsair drive I can max out the bandwidth.


HI. did you end up buying the gen 4 drive . i'm thinking of buying samsung evo plus . But i remmembered that most of the sata interfaces where backwards compatible. So it got me thinking , maybe a gen 4 x4 m.2 nvme drive will work in gen slot ?


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## LFaWolf (Dec 28, 2019)

lamonz88 said:


> HI. did you end up buying the gen 4 drive . i'm thinking of buying samsung evo plus . But i remmembered that most of the sata interfaces where backwards compatible. So it got me thinking , maybe a gen 4 x4 m.2 nvme drive will work in gen slot ?


I ended up buying a few 2tb drives -Samsung 970 evo plus, Corsair mp600, silicon power p34a80, and hp ex950. Yes the mp600 is backward compatible and works in an x299 motherboard. X299 is gen 3 only


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## lamonz88 (Dec 28, 2019)

LFaWolf said:


> I ended up buying a few 2tb drives -Samsung 970 evo plus, Corsair mp600, silicon power p34a80, and hp ex950. Yes the mp600 is backward compatible and works in an x299 motherboard. X299 is gen 3 only


I have a Laptop with LGA 1151 socket motherboard running 8700 cpu with soldered on Nvidia 1600 if i remember correctly and as for storage it's got Two (2) x4 Gen 3.0  slots .! Does the Corsair drive on your PC maxes out the the gen 3 slot...? How is the bottom line on crystalDiskMark , is it close to gen4 published results.?


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## LFaWolf (Dec 28, 2019)

On an empty drive my mp600 reaches the posted speed in crystal diskmark, so it was very close to max out the gen3 bandwidth. All of the drives, unless you are running benchmarks, feel very fast to me, much faster than my 860 sata ssd. Boot to Windows in about 15 seconds


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## lamonz88 (Dec 28, 2019)

LFaWolf said:


> On an empty drive my mp600 reaches the posted speed in crystal diskmark, so it was very close to max out the gen3 bandwidth. All of the drives, unless you are running benchmarks, feel very fast to me, much faster than my 860 sata ssd. Boot to Windows in about 15 seconds


Thank you for your reply. Now i can go ahead with my purchase. i think ill be getting a 1TB Seagate FireCuda 520, 
M.2 (2280) PCIe 4.0 (x4) NVMe SSD, Here in UK i'ts only £200 and i'ts got low profile heat sink , just what i need for a laptop . 
as a thank's  i can highly reccomend A Primo Cache to speed up your Pc even more. I will attach a screenshots of CrystalDisk Benchmarks with Primo Cache ON and OFF . I'm runnig a single Samsung EVO 970 250gb m.2 nvme SSD . In first image you can see Samsung Magician Software . I benchmark  it with Primo Cash ON . in next image you wil see Top right a results for my drive with PriCache on and bottom right with PrimoCache OFF . 









If you need any help setting up the software , please ask .. There's 30 day trial , but for what you get and only 30 usd . Can't beat that .


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