Discussion disable NVMe drive in BIOS - motherboard support

[MG2]

You might have wanted to disable or disconnect an M.2 drive, for whatever reason. Maybe for installing a different OS or for testing or privacy purposes...
Unfortunately, while motherboards often let you disable SATA ports, support for disabling M.2 slots in BIOS is almost non-existant.

So, I have contacted motherboard manufacturers regarding this feature and I want to share my findings.

ASUS informed me that their Z690 line has some limited support for this: it lets you enable/disable one M.2 slot. Looking at the manual, it's the one from the chipset.

ASRock doesn't have this as a standard feature, but they told me I can contact them and they'll send me a custom BIOS for my mobo with this feature enabled. And it would work even on older models, like AMD B450 and Intel Z490. They didn't say anything about it being limited to specific M.2 slots (like in the Asus case), but they did say it wouldn't work on PCIe slots with PCIe-M.2 adapters.

Gigabyte just gave me a standard answer that they'll consider it. MSI and Biostar didn't reply so far.

So, if anyone has an ASRock mobo and is interested in this feature, please contact them and let us know how it goes. Those with newer ASUS boards can also try it for that one slot.
And it would also help if more people request this feature from motherboard manufacturers. I think it should be standard and it's more needed for M.2 than for SATA drives, because the former are harder to physically disconnect.

 

[sdifox]

Err PCIe is direct to CPU. The ones you can disable is probably provided through chipset.

 

[igor_kavinski]

Err PCIe is direct to CPU.

Why would it be hard to disable an M.2 slot connected to the CPU?

Just curious because your reply sounds like you know a bit more about this and maybe the specific reason?

 

[sdifox]

Why would it be hard to disable an M.2 slot connected to the CPU?

Just curious because your reply sounds like you know a bit more about this and maybe the specific reason?

The whole point to PCIe connection is to minimize delay. Adding anything else there to disrupt the connection is counter productive. Op is better off removing the nvme drive to do what he wants. Or change bios boot order setting and remove the drive from the list.

 

[igor_kavinski]

The whole point to PCIe connection is to minimize delay.

Interesting thought. Are there any benchmarks that compare the latency between CPU PCIe and chipset PCIe M.2 slots?

 

[sdifox]

Interesting thought. Are there any benchmarks that compare the latency between CPU PCIe and chipset PCIe M.2 slots?

I don't know. I imagine it depends on implementation and hardware limitation.

 

[OlyAR15]

Yes, it is such a good idea to go to the expense and trouble of buying and installing an M2 drive, only to not use it. Makes perfect sense. Why didn't anyone think of this before?

 

[zir_blazer]

The whole point to PCIe connection is to minimize delay. Adding anything else there to disrupt the connection is counter productive.

This is one of the worst descriptions about how things works that I have ever read...

Intel 12th Generation Intel Core Processor Datasheet Volume 2 of 2 mentions at section 6.24 Link Control (LCTL) for the D6:F0 Device (The PCIe Root Port that controls the 4x lanes that are usually going to the Processor attached M.2 Slot) that there is a Link Disable (LD) Bit that actually disables it (And most likely it is PCI Express standard, so I expect every existing PCIe Root Port to support it). So a BIOS option to disable that specific Port would just need to flip that Bit.

And yes, there are use cases where you may want to disable a PCIe NVMe SSD without physically removing it.

 

[sdifox]

Isn't that for ASPM active state power management?

https://en.m.wikipedia.org/wiki/Active_State_Power_Management

<----- most definitely not an expert

 

[zir_blazer]

Isn't that for ASPM active state power management?

https://en.m.wikipedia.org/wiki/Active_State_Power_Management

No, ASPM is separate.

PCI: Add sysfs attribute for disabling PCIe link to downstream component - Patchwork

PCIe root and downstream ports have link control register that can be
used disable the link from software. This can be useful for instance
when performing "software" hotplug on systems that do not support real
PCIe/ACPI hotplug.

Configuring specific PCIe devices

Device Disable
Auto—The device is automatically enabled at server boot.
Disabled—The device is not automatically enabled.

PCIe Power Management (ASPM)
Auto
Disabled
L1 Enabled—The device's link enters a lower power standby state at the expense of a longer exit latency.

 

[sdifox]

No, ASPM is separate.

PCI: Add sysfs attribute for disabling PCIe link to downstream component - Patchwork

Configuring specific PCIe devices

that's on proliant servers no? servers tend to have better configuration flexibility.

 

[MG2]

The ASRock rep confirmed that their custom BIOS works for disabling any M.2 slot, including those from the CPU. And as I said in the OP, they told me it would work on every new-ish motherboard.

ASUS mobos are limited to the chipset slot only currently. But I imagine they and all other manufacturers could also enable it for other slots with a new BIOS. Unless ASRock added some special hardware tweaks that allows them to do this, but I doubt that's the case.

 

[MG2]

Meanwhile, I found this option also in the ASUS Intel 700 series manual, in the same section (PCH Storage Configuration) as for Z690, but with one difference:

I hope that's just an error and that the toggle isn't limited to SATA M.2 drives.

 

[raywood1]

I am using AMI BIOS 2.16.1240 (dated 2015) on an ASUS H97-PLUS motherboard. In the BIOS, I go to Advanced > PCH Storage Configuration > SATA (SATA 5,6) and M.2 Configuration.

It offers a choice among Auto, SATA, or M.2. I choose SATA > F10 > Enter. On reboot, the system returns to BIOS. It appears not to find a bootable operating system. If I change that choice from SATA to Auto or M.2, the system reboots into the Windows 10 installation on the M.2 drive.

With that item set to SATA, I boot a live Ubuntu USB drive. It boots by default; I don't have to select it in BIOS. In Ubuntu, I open the Disks program and look at the drives listed. It does not list the M.2 drive. I reboot, change SATA back to M.2, select the Ubuntu USB, and boot into Ubuntu again. Now Disks does list the M.2 drive.

This PCH Storage Configuration setting appears to offer the kind of solution the OP is looking for. Does this option not exist in other BIOSes - or did AMI remove it sometime after 2015 - or is it just hard to find?

 

[MG2]

@raywood1: I'm not sure, but I think on most motherboards the switching between SATA and PCIe/M.2 when lanes are limited happens automatically, with the mobo prioritizing one or the other when both are plugged in. It looks like ASUS gives users some more control there.
Also, it's usually only available on PCH/chipset slots, which is less than ideal.

 

[MG2]

Meanwhile, I looked at the remaining motherboard manufacturers and this is what I found:

EVGA appears to have full control on enabling/disabling all M.2 slots, according to the manuals.

For example, this is from an X570 manual:


And this is from a Z790 manual:



Biostar informed me that there's no such feature on their boards.
MSI support in their very broken English tried to tell me that they support it, but I think they meant it for SATA ports. I asked someone with a MSI board to check and he said there's no such option for M.2 slots in the BIOS.

So, right now, EVGA mobos seem to be the best choice in this regard.