Optiplex 5090 11th Gen PCIe 4.0 SSD

5090 uses Q570 rocket lake chipset.  The top chipset in this Intel 500 series is Z590.  This is what I read:

The Z590 chipset natively supports the PCIe 4.0 standard (a first for Intel).
Here is the catch:  the Chipset doesn’t seem to provide PCIe 4.0 lanes, but instead 24 PCIe 3.0 Lanes. What native support really means is that it can relay the 20 PCIe 4.0 lanes nested in the CPU.

Intel Rocket Lake: PCI-Express 4.0 makes its debut. The processor features a 28-lane PCIe root complex. 16 of these go to the the main x16 graphics slot, 4 toward an M.2 NVMe Gen 4 slot that's wired directly to the processor, and 8 toward the DMI x8 chipset-bus. These lanes still operate at PCIe Gen 3 bandwidth, as the 500-series PCH doesn't support Gen 4.

Confirmed: Q570 and Z590 both have PCIe revision 3.0.  Not 4.0

Dell 5090 tech sheet:

tower: Gen 4 PCIe

SFF: Gen 3 PCIe

If you install 980 in the M.2 slot which directly connects to cpu, it should run at 4.0 speed.  at this point no insight why you only got 3.0 speed.  

Rocket lake
when you install 980 in PCIex16 slot, it goes through M.2 to PCIe adapter interface.  not sure if the adapter is the bottleneck.  also do you have 5090 MT or SFF?  SFF x16 slot is Gen3.

to install OS on PCIe NVMe ssd and make it bootable, try Dell method 3

1. Ensure the latest compatible version of a UEFI BIOS is installed on your PC.

2. Set the Boot Order list in your BIOS so that the Windows Installation Media source is first. (Be that a thumb drive or optical drive.)

3. Save and Exit the BIOS and the Windows installation should begin.

4. On the Where do you want to install Windows? prompt :

   • If the SSD is listed, select it and click next.

   • If the SSD isn't listed then :

     1. Click Load Driver

     2. Navigate to the location you have saved the file from the manufacturer.

     3. Select the file and load it.

5. Your SSD should now be listed, select it and click on next.

6. Follow the remainder of the installation instructions until the install is complete.

7. In the BIOS set the SSD to be the Primary Boot device.

8. Save and Exit the BIOS.

9. Boot to Windows and open the Device Manager for your OS Version.

10. Under Storage Controllers find your device and right click on it and select Update Driver Software.

11. Navigate to where you have saved the latest version and load it.

12. Reboot your PC to finalize the installation.

Thank you for asking for clarification/more details

Regarding the model: The 5090 is a Tower and not a SFF, so it should support Gen4 on both the M.2 slot and the 16x slot if I'm understanding it right.

Regarding the 980 Pro in the M.2 Slot: The machine installs and boots off of the NVMe SSD when it's installed into the M.2 slot. I've installed Windows onto the Samsung 980 Pro in that M.2 slot as well as restored the image of the original drive that came with the PC on to it. Both installs (factory and fresh) result in PCIe 3.0 speeds of the drive which is roughly 3500 MB/s for both read write. My understanding is that I should see around 6500 MB/s on the read speeds and 5000 MB/s on the writes on PCIe 4.0 with this SSD.

Regarding the 16x PCIe NVMe adapter: The adapter could be a bottlekneck as you suggest. It doesn't specifically say it's a 3.0 adapter, but I'll order one that specifically IS a PCIe 4.0 specific adapter and check that and report back.

Unfortunately, even if I got the full speed out of it, this Optiplex 5090 will not recognize the drive in the 16x slot in the BIOS, so it can't be selected as a boot option like previous Optiplex models were able to do.

Thanks for engaging in the discussion.

try verify that same 980 in PCIe adapter can be detected in 3080 optiplex as boot drive. If so, compare 3080 bios settings with 5090.  Lastly, clear CMOs settings in 5090 and try again.

Thanks redxps630.

I can confirm that the PCIe adapter is detected in the 3080 BIOS and it's selectable as a boot drive. The 5090 does not list it.

Per your request, I cleared the CMOS on the 5090. BIOS still does not see the drive in the PCIe adapter as an available drive (again, to be clear, it sees it fine in the M.2 slot) and in the boot manager section of the BIOS when trying to navigate to a boot file, the drive is not seen as a location as if there is no drive there. However, just as before, it is seen in the OS if for example I boot the 5090 from my Samsung 970 Pro NVMe drive in the M.2 slot and leave the 980 Pro in the PCIe adapter in the 16x slot. My Macrium Reflect boot USB can see the 980 Pro and so can my Windows 10 USB made from the Media Creation Tool. Everything can see the 980 Pro in the 16x slot adapter except the BIOS.

By the way, I have tried it in both AHCI and RAID mode.

Strange indeed...

This may possibly be a 5090 bios bug that has not been fixed yet despite bios being the latest version.  The 5090 500 series platform is a significant improvement over the 3080 400 series and quite new along with the rocket lake cpu.  It is possible that the bios engineers have not ironed out all the details.  If so nothing you can do except waiting for the next bios release which hopefully may solve the issues.

That sounds likely. I'm going to test the new PCIe adapter that's coming and I'll report back.

If a BIOS update comes out that somehow enables PCIe 4.0 speed on the M.2 slot, I'll report back on that as well.

Thanks for engaging with me on this.

Thank you for providing the interesting case in point.

I got the new PCIe 4.0 NVMe adapter in. Made no difference.

The BIOS will not see the drive when it's in the adapter to boot off of.

When booted off of another Samsung 980 Pro in the M.2 slot (C drive) and having a second 980 Pro in the PCIe full length x16 slot (D drive), they get the same read/write numbers - neither of which is PCIe 4.0 speed.

I'm going to do some more testing with the SSD both in the M.2 slot and the PCIe adapter in a new 11th gen PC that came in today to see if I get what I expect out of it. I'll post the details of the other PC and the results.

980 Pro in the M.2 Slot980 Pro in the PCIe full length adapter

Something I didn't mention before is that I ordered 2 new PCIe adapters, 1 that is the full length x16 slot like my old one, and one x4 slot version.

I just tried the x4 slot version and THAT one the BIOS seems to like. It can see the drive and it can boot off of it.

So, in the boot manager of the BIOS, it CANNOT see the adapter in the x16 slot, but it CAN see the adapter in the x4 slot.

However, booting off of the x4 adapter has the exact same results as the M.2 slot and the x16 slot (non-boot) where it's running at 3.0 speed as you can see from the screen captures above.

Here is a link to the x4 adapter that the BIOS is happy with:
AMPCOM M.2 NVME SSD to PCIe 4.0 Adapter Card
https://www.amazon.com/gp/product/B0876MLNY6

I still want my 980 Pro to run at ~6500 / ~5000 MBps R/W because that's what I paid for between the 11th gen PC and the PCIe 4.0 SSD. I'll update this post if Dell ever releases a BIOS update that actually makes the board function at 4.0 speeds.

When I look at Samsung 980 Pro benchmark, it seems 3000 is about the max sequential R/W speed.  Am I missing something?

980 Pro

https://ssd.userbenchmark.com/SpeedTest/1307906/Samsung-SSD-980-PRO-500GB

If you read a bit, you may realize the Samsung spec speed is the best case scenario. Actual operational speed varies a lot depending on multiple factors. The issue appears to be related to Samsung, not Dell 7090 bios.

https://linustechtips.com/topic/1262379-samsung-980-pro-1tb-slow-write-speeds/

PS only the x16 slot is directly connected to cpu PCIe 4.0 lane.  the x4 slot is connected to chipset PCIe 3.0 lane.

Well, you can't really trust Userbenchmark on this because we have no idea if the users have a PCIe 4.0 motherboard and 11th gen Intel chip or the equivalent AMD chip to push the drive to it's max potential.

Also, most of the discussions around SSD speeds being slow are due to the chips getting full/heavily used over time. These are two brand new 980 Pro's (whose lifespan info is in the screenshots I shared) that should run at full speed. Benchmarks all over the place including ones linked in the Linus thread you linked that show full advertised speed.

The original thread post in the one you linked for example has 3 historical tests in his screenshot. The first one on 10/16/2020 shows a read of 7037 MB/s (in fact, all of his tests show numbers over 7k) and his write which was 5168 MB/s on 10/16 had dropped to 2246 MB/s 9 days later and he's trying to find out why. Hence the discussion about time, cache, trimming, resetting, etc that follows that discussion.

My drives are brand new in a brand new 11th gen PC and I should be seeing numbers over 3500 particularly for the read which is what I'm mostly interested in. No, this isn't Samsung's issue. Something is wrong here with the 5090.

By the way, now that I've tested all of the PCIe slots and not seeing any difference between them, the drive is back in the M.2 slot and will stay there for future testing.

I'm hoping to test the 980 Pro in this other 11th gen PC that came in yesterday. I'll report back on that as soon as I do.

As quick as that was, I popped the 980 Pro in the M.2 slot of this other PC (Asus i9 11900) and here are the results:

Those are acceptable PCIe 4.0 numbers in an SSD like this.

If I would have bought a Precision, XPS or an Alienware, I wonder if I'd have the same speed issue as with this Optiplex? That's conjecture for another day, but for now, definitely 100% something not right with this 5090 motherboard/BIOS.

It's not isolated to this PC either. I have 3 of these 5090 11th gen i7 11700 towers here and they all do the same thing.

I think that proves it. Thank you for the update.

Interesting read.