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January 15th, 2024 21:13

Considering moving NVME in 7865 from Flexbay to motherboard

Hello Dell Community; this is my first post, so please be nice :)

I recently bought a Precision 7865 tower with a dual M2 flexbay; the first slot has the only storage device, a Kingston SNV2S/1000G; this is a 1TB M.2 2280 PCIe 4.0 NVMe Gen 4 x 4 device. I would have thought the SSD would be faster on one of the motherboard M2 slots than in the flexbay connected by a cable, so am considering moving the device there.

Is this generally a thing worth doing, or is any speed-up likely to be minimal?

(For context, I am not the very first owner of the machine, so had no say in the original configuration decisions; why the boot/os SSD would be in the flexbay and not on the motherboard in the first place, I have no idea).

Any guidance welcome - thanks :)

5 Practitioner


5.5K Posts

January 16th, 2024 08:06

The flexbay and onboard M.2 slots are both PCIe Gen 4.  There will be no performance speed gain by moving to M.2 slots.  Technical specs for internal slots and storage are below.


4 Posts

January 16th, 2024 08:40

Thanks for that.

I was concerned that the cables (think inductance, capacitance, transmission lines, etc.) from the flexbays in getting to the motherboard, vs a direct connection on it, would have an effect; I know next to nothing about analogue electronics, so wondered if that could have any effect beyond negligible. But it now seems I was Googling for the wrong thing - NVME and M2 rather than PCI4; it seems there are PCI4 riser cables that people use with graphics cards; some of these are 20cm long and apparently the length does not affect the performance.

The cables to the flexbays are about that length, so it appears such effects are negligible. Job done.

(Thought I will buy a better SSD at some point; the one the machine came with is rather slow; approx. 3000 R/W speed; some, e.g. Samsung EVO PRO, are twice as fast).


5 Practitioner


5.5K Posts

January 16th, 2024 10:16

My post was offered the published storage specification for the 7865 system.  Description for M.2 and the value of NVMe drives from both connectors are the same PCIe Gen 4.  Base on that, I would say the performance of NVMe in flexbay and M.2 slot will be the same.  Thought that it may help with saving you time from switch drive back and forth.

You have not provided any baseline or performance number for your comparison.  You will need to have some kind of numbers for measure.  When in doubt, just run a drive performance test.  Download and install Crystal Disk Mark, a storage benchmark utility, running a test with SSD drive in flexbay then move the drive to an onboard M.2 slot, then run another test.  You will then, seeing the performance result.

For your SSD shopping suggestion, note that benchmark results are artificial.  I would paid more for enterprise grade for sustained speed and endurance, not for top benchmark speed.  Depending on the type of job or usage, also taking DWPD into account.


4 Posts

January 17th, 2024 20:38

@Chino de Oro​ Thank you for your advice; as it happens, I'd already ordered the Samsung drive before reading that; while benchmarks are always somewhat suspect, pretty much every review indicates that it is among the very best of the PCIE 4 capable M2 drives.

For clarity, after many years of using and configuring preloved Dell machines, and having had an opportunity to buy the machine new for a very good price, I bought it as a home computer, so enterprise considerations don't apply. This is not my first time using a Dell Precision in this way, but it is the first time with such a modern one :)

Thanks again for your comments.

4 Posts

January 29th, 2024 21:43

PS: For the handful of people in similar situations to mine, replacing the Kingston SSD with the Samsung yielded an immediate and noticeable performance improvement for disk based activities. Since it only cost £100, it turned out to be a cheap upgrade that was worth doing. This only applies to oddballs, like myself, who are using a machine of this class as a home / gaming computer; but for what it's worth, there it is.

As it turned out I did move the SSDs to the motherboard, but for other reasons; later on I want to fit an optical drive and this would have consequences for the flexbays; however, that's a story for another thread.

6 Professor


7.9K Posts

January 31st, 2024 03:53

No surprise that the Samsung SSD turned out better than the Kingston.  :)


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