X570 WARNING: DMAr PRO-SKU feature can prevent motherboards from booting until you change CPUs

aBav.Normie-Pleb · September 28, 2020, 7:08pm

WARNING: DON’T TRY THIS AT HOME IF YOU DON’T HAVE THE MEANS TO MANUALLY REFLASH THE BIOS

Hi,

I’ve recently gotten a Ryzen 7 PRO 4750G for testing purposes and installed it in an ASUS Pro WS X570-ACE with the latest UEFI 2206 first (2 x 32 GiB Micron DDR4-3200 ECC UDIMM, nothing else except a PSU).
That UEFI version officially supports this Renoir Zen 2 APU (currently not available through general retail channels but you can get it through OEM resellers without warranty).

Everthing working fine (no PCIe components installed, display via motherboard HDMI, only an USB keyboard and mouse connected to the motherboard).

I then go into the UEFI -> Advanced -> AMD CBS -> NBIO Common Options:

(1) IOMMU: Auto -> Enabled -> All OK after reboot

(2) DMAr Support: Auto -> Enabled - USB devices no longer working (mouse/keyboard etc.) after reboot

After a reboot during POST the motherboard states that no keyboard is detected and I am to press F1 to enter BIOS

(3) No biggy, I had thought at first: CMOS Reset -> No effect

(4) Medium biggy, I then thought: Remove the CMOS battery and wait an hour -> NO EFFECT

Sh…, I mean big biggy. Contacted ASUS Support about this - no response yet.

(5) Kept every component and changed the motherboard model to an ASRock X570 Taichi with the USB Flashback feature, also with the latest UEFI (P3.40) that supports that APU officially, too.

(6) Did the same UEFI setting changes, and the board doesn’t recognize any USB devices either.

(7) CMOS reset and removal of battery again without any effect.

(8) BUT: After reflashing the BIOS via USB Flashback when the system was still turned off but connected to a PSU the motherboard POSTs again normally.

Is this a bug or a feature?

I’ve read the story about locking EPYC CPUs to certain server vendors but not UEFI options permanently bricking an UEFI…?

Hope that maybe I can spare someone this unpleasant experience (“Hmmm, DMAr Support - Enable DMAr system protection during POST. - That sounds helpful!”)

Regards,
aBavarian Normie-Pleb

GigaBusterEXE · September 28, 2020, 8:28pm

USB keyboard or PS2

aBav.Normie-Pleb · September 28, 2020, 9:00pm

The ASUS Pro WS X570-ACE does unfortunately not have a PS/2 connector.

I’ve also tried installing a dedicated PCIe Sonnet Allegro Pro USB3-PRO-4PM-E USB controller AIC with 4 x Fesco Logic USB 3.0 chipsets.

The ASUS Pro WS X570-ACE boots in UEFI-only mode by CMOS defaults. In UEFI mode you can attach mouse and keyboard to an USB AIC and they (normally) already work prior to the booting of the OS.

Doesn’t work either.

Maybe new rabbit hole for @wendell ?

wendell · September 28, 2020, 10:16pm

What are you looking to do with dmar? It’s interesting it bricks the motherboard. I don’t even have the dmar option on mine.

Riotvan · September 28, 2020, 10:22pm

Maybe it messes with the system management stuff on the cpu?

aBav.Normie-Pleb · September 28, 2020, 10:24pm

Strange that you can’t see this option, do you have IOMMU changed from Auto to Enabled?

Right now I don’t even know what DMAr actually does, I just thought that it sounded interesting (appeared after IOMMU is changed to enabled) and decided to poke at it with a stick

wendell · September 28, 2020, 10:27pm

Yes. Maybe an apu specifc thing… I have a similar bios as you but it’s hacked up for one of my own projects.

aBav.Normie-Pleb · September 28, 2020, 10:32pm

Could be, the SKU I’m using is a PRO variant and these have some extra features (or not disabled) like that VM memory encryption.

d3vnul · October 1, 2020, 4:30pm

That would only be available if you have IOMMU enabled.
dmar -> direct memory access remapping

How about making a bootable usb drive , freedos , and reflash the bios with an autoexec script and “flashrom”. org

I have the same motherboard and successfully flashed custom rom. You can find details/tutorial about this at winraid.

Hope i didn’t brake any rule , only registered to offer my reply. Hope it helps.

Update: Thinking more about it , it wont work i guess because this method would had required setting CSM enabled on bios for the bios reflash … and as you have no input …

aBav.Normie-Pleb · October 1, 2020, 4:40pm

Booting the ASUS board is impossible since it stops right after the POST with “No keyboard detected, press F1 to enter BIOS”.

USB devices in general don’t show up (0 USB devices, normally you see something like “1 mouse, 1 keyboard, drive” etc.

I guess ASUS’ crucial mistake here is that the option “stop boot if no keyboard is detected” is the CMOS Default BIOS setting and it does not get automatically disabled if DMAr is enabled.

On the other hand if I read the fragments about what DMAr actually is good for correctly, it is intended that as many controllers as possible (that have direct memory access) are not initialized during POST like they normally are, instead only after a proper OS is booted it then “securely” initializes these controllers with remapped memory segments (?).

Is it true that some AMD CBS options are saved to non-volatile space on the BIOS chip in general?

That would explain why a CMOS Reset did nothing for me and only “USB Flashbacking” was able to bring the ASRock X570 Taichi back to normal operation.

d3vnul · October 1, 2020, 4:44pm

I better understand the situation now. No luck for a reply from Asus yet ?
Hope you don’t mind asking , but how did you do the CMOS Reset ? I do not imply that you haven’t done it proper , but just for my mind picture , would like to hear it from you.

aBav.Normie-Pleb · October 1, 2020, 4:50pm

The ASRock X570 Taichi has a CMOS Reset button at the back i/O shield.

My method for CMOS reset there:

Unplug AC power cord from wall
Press Power On Button on case for 10 sec
Remove BIOS Battery
Press CMOS Reset Button at I/O shield for 10 sec
Reseat BIOS battery, connect AC power and try again

(No change)

Then I used the USB Flashback feature to reflash the BIOS and the motherboard operates normally again.

The ASUS board does not have a CMOS Reset button on the back I/O shield, I was pretty pissed, so I removed the BIOS battery over night (about 8 h) and tried again the next morning (PSU also disconnected).

d3vnul · October 1, 2020, 4:59pm

Have you tried Shorting the jumper on the motherboard after AC unplug ?
I did this a few times yesterday , playing with ram oc. And i recall that every time i would short the jumper , the cpu boot led check would be active for a second (red). Just want to make sure that happens for you when you Clear Cmos with by Shorting the cmos jumper.

aBav.Normie-Pleb · October 1, 2020, 5:09pm

Have not tried the CLRTC jumper yet (access was blocked in build), will try this later today and report back.

If you discharge all capacitors by pressing Power On for a few seconds on a system with a disconnected PSU you’ll never see any LED lighting up again.

(this usually only happens if you have just unplugged an active PSU and some parts have a remaining charge that is then drained)

d3vnul · October 1, 2020, 5:11pm

You are perfectly right , i like to see the drain
It would be mega super dumb if this is unfixable , can’t see a reason why something like your issue would still occur after a successful cmos clear.

aBav.Normie-Pleb · October 1, 2020, 6:37pm

Question in the meantime:

What CPU are you using on your Pro WS X570-ACE and do you see the DMAr Support option, too?

GigaBusterEXE · October 1, 2020, 6:40pm

I always jump the clear cmos or use clear CMOS button while the computer is plugged in and the PSU switch is set to on, I only unplug to do the battery removal, I’ve encountered some mobos that keep settings after battery removal so that’s why I like to use the jumper

If I do a lot of fiddling with the board I like to hook up the reset button on the case to the jumper

aBav.Normie-Pleb · October 1, 2020, 6:46pm

That had been my previous modus operandi until I made the aquaintance of the ASRock Rack X470D4U (sarcastic, non-COVID-19 cough)…

There sometimes only after removing the battery for a while and disconnecting the PSU you were able to let it POST again.

But will definitely hook up extension wires to these jumper pins from now on on every motherboard that doesn’t have a proper CMOS reset button.

d3vnul · October 1, 2020, 7:44pm

I have a Ryzen 3600 at the moment. I just enabled IOMMU and booted to win just fine. No sign of DMAr.
I’m thinking what will happen in your case if you can try to boot with a non Pro CPU , which probably doesn’t support this DMAr option. I’m also using latest 2206 Bios version. I have exported my bios settings to a txt file , but i had no time to get familiar with this forum rules , so I’m not sure if i can post the long list of bios config here or provide a link ?

aBav.Normie-Pleb · October 1, 2020, 8:25pm

THAT MIGHT BE A WORKAROUND TO FIX THE BOARD’S BIOS =)

[SOLUTION] Put a non-PRO SKU in there that doesn’t support DMAr, it should boot fine with regained USB functionality. Load UEFI defaults via UEFI GUI, save, reboot and pop the PRO SKU back in. [/SOLUTION]

To be sure:

Is there a way to manually reflash the complete BIOS with an USB thumb drive?
(Have never looked into that)

ASUS unfortunately just checks if the BIOS version you select as a file is the same one as installed and then pretends to flash (process is completed much too quickly).

With the ASRock board you can actually reflash the same BIOS version as the one that’s already installed via the UEFI GUI (takes much longer and an additional indicator is the activity LED on the USB thumb drive itself).