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No video output from APU when GPU present

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mizzack View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mizzack Quote  Post ReplyReply Direct Link To This Post Topic: No video output from APU when GPU present
    Posted: 30 Sep 2017 at 11:02pm
Hi,

I've got a X370 Gaming K4 with A8-9600 APU installed.

The HDMI output on the board works correctly and outputs video as expected when all PCIE slots are empty. However, when a dGPU is installed, the onboard graphics gets disabled completely in favor of the dGPU (no output from mobo HDMI and lspci no longer shows the onboard VGA controller).

There doesn't seem to be any option to prefer onboard video within the UEFI either.

This is a problem because I need the onboard to work for PCI passthrough.

Is this by design? The manual makes no mention of this crippling limitation.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote parsec Quote  Post ReplyReply Direct Link To This Post Posted: 30 Sep 2017 at 11:47pm
Originally posted by mizzack mizzack wrote:

Hi,

I've got a X370 Gaming K4 with A8-9600 APU installed.

The HDMI output on the board works correctly and outputs video as expected when all PCIE slots are empty. However, when a dGPU is installed, the onboard graphics gets disabled completely in favor of the dGPU (no output from mobo HDMI and lspci no longer shows the onboard VGA controller).

There doesn't seem to be any option to prefer onboard video within the UEFI either.

This is a problem because I need the onboard to work for PCI passthrough.

Is this by design? The manual makes no mention of this crippling limitation.


Which UEFI/BIOS version do you have installed?

I cannot be certain this would make a difference, since I don't have a Ryzen APU processor installed in my different ASRock X370 board, but the 3.10 UEFI version for your board has this description:

Add AMD PBS Primary Video Adapter to control Bristol Ridge CPU display order.

http://www.asrock.com/mb/AMD/Fatal1ty%20X370%20Gaming%20K4/index.asp#BIOS

That sounds like an option for selecting the video source, but I could be wrong. I have the equivalent UEFI version installed in my X370 board, but use a Ryzen 7 1700X. I haven't noticed an option in the UEFI for video source selection, but since that option would not apply with my CPU, it may not be shown in that situation.

Intel mother boards, with most of their processors having an iGPU, have had UEFI options to select the Primary Graphics Adapter, as well as enable the iGPU while the dGPU is in use, for years. I assume the same would be possible with AM4 boards.

I don't know where this UEFI option would be located in an AM4 board's UEFI. Possibly in the NB (North Bridge) Configuration screen in the Advanced section, or buried somewhere in the many Advanced\AMD CBS screens, such as NBIO Common Options.

The Ryzen manuals don't reflect the current state of a Ryzen board's UEFI options or features, which have been evolving along with things like new AGESA versions from AMD.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Xaltar Quote  Post ReplyReply Direct Link To This Post Posted: 01 Oct 2017 at 12:13am
Check in your UEFI for a "Shared memory" setting, if you find one set it to anything other than auto or disabled and your iGPU should enable.

If not (I can't check as I don't have an APU for my Gaming K4) then I have no idea. Parsec's info looks promising too. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mizzack Quote  Post ReplyReply Direct Link To This Post Posted: 01 Oct 2017 at 1:19am
Good catch on those BIOS notes. I'm running 3.30, though. Perhaps 3.10 was on a different branch and those options aren't available in 3.30...

Also re: shared memory, I have it set to 2GB but it gets reset to 1GB on reboot.

I'll look into downgrading and keep tinkering.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mizzack Quote  Post ReplyReply Direct Link To This Post Posted: 01 Oct 2017 at 3:11am
Ok, no luck with 3.10 or changing shared mem size.

I threw the APU in my main X370 board (Prime X370) and it has options for primary display as well as multiple display devices (not to mention OC functionality!) 

Between this and the EOL/RAM limitations with the Gaming K4 I can't say I'm impressed with ASRock here... I guess I'm gonna ditch this board and grab a cheap Asus B350
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