Relative Performance of Two x86_64 Devices

1st Official Post

    Hello

    I have two old-ish devices which I am trying to assess the relative merits of:-

    Compulab Fitlet-RM (AMD "Mullins" A10 Micro-6700T quad core APU nominal 1.2 GHz, 4 GB DDR3L-1333 RAM, Radeon R6 integrated graphics), circa 2014

    Zotac PI225-GK (Intel Gemini Lake N4000 dual core SoC nominal 1.1 GHz, 4 GB DDR4L-1866 RAM, Intel UHD Graphics 600 integrated graphics), circa 2017

    Both were designed for low power environments, are fanless and are specced to use less than 14 W under load.

    I have tried booting up the latest version of LibreELEC 10.0 from a suitable micro SD card with each device connected to the same monitor.

    The Zotac seems to struggle with the interface and most video playback. It's hard to describe, but it just seems "choppy", though with the debug mode on neither of the two cores is getting used above 20% and FPS averages 32.

    The older Fitlet seems much happier as the interface moves fluidly and 1080p playback is perfect. I recall I used to have trouble with graphics support, but haven't used the device for a while so presumably the AMD driver was improved.

    Neither is particularly good at 4K H.264 AVC playback, though I am only using a 1080p monitor.

    I am particularly interested in working out if there are settings that I need to change to make the Zotac work better, because reading the forum there are indications that some of the devs have targeted Gemini Lake specifically.

    Though the Zotac has the "cool" factor of being smaller than the average mobile phone, and can run off 5V USB power, I am under no illusions about its limitations, having spent a while trying to get a working Wayland desktop on it and not being particularly happy... :-/

    So that I understand my position, should the newer Intel-based device be faster for LibreELEC?

    • Official Post

    I'm kinda surprised about the Zotac box, as I have a Gemini Lake HD605 board, which doesn't seem to have hiccups.

    FYI, 4K/h264 is a video combination that is not supported well by graphics cards. The consensus is that 4K is to be coupled with the h265 format, and that combo will be played fine on 99% of all recent video cards via hardware acceleration.

    "Faster" is not the description I would use. There is the Kodi GUI display, and the playing of the actual video. All Intel (U)HD6xx cards should render the Kodi GUI pretty flawless, no matter which CPU is involved. A slow/low-powered CPU such as the N4000 will do certain things perhaps less 'nippy', but that is because it is simply not a 16-core monster.

    Video display being 'choppy' could be the result of certain settings in Kodi, but we'd need to see the debug log first to make final conclusions.

    I tried tinkering about with some of the i915 module settings (disabling framebuffer compression, because there are reports that it doesn't work properly on Gemini Lake, etc.) but didn't see any improvement.

    Then I tried something a bit more drastic: blacklist snd_hda_intel.

    (The monitor that I am connecting to doesn't have any audio outputs. I use a separate USB dongle for headphones)

    Suddenly, everything is 100% smooth on the Zotac. 8)

    And I still get synchronised audio through USB.

    How should I handle this? Is HDMI audio broken?

    • Official Post

    I had almost forgotten about it, but I had to 'change/downgrade' the Intel graphics in LibreELEC and in Ubuntu 20.04 on the Gemini Lake box. Implementing LIBVA_DRIVER_NAME="i965" makes the decoding of h265 graphics work as it should.

    So the problem is definitely HDMI audio.

    I have tried numerous kernel parameters in /LIBREELEC/EFI/BOOT/grub.cfg, nothing seemed to make any difference.

    It's clear when it won't work properly, because when I select a video to play, it briefly shows the "loading" circles and un-dimms the screen, nothing happens, then the circles return for exactly 3 seconds, before the video begins, plays a bit choppily for about 5 seconds and then freezes (one of the CPU cores goes to 100% at this point). The interface still works and I can back out of the video.

    As a workaround, I created /STORAGE/.config/modprobe.d/disable_hdmi_audio.conf, with the contents:-

    blacklist snd_hda_intel

    Rebooting with this in place, LibreELEC plays the same videos without any problem, though obviously this limits its use as a portable device as there will be no sound when connected to TVs and I will need to carry a USB dongle everywhere for an alternative.

    Funnily enough, this used to be the problem with the Fitlet device, but seemingly got fixed in the radeon driver since then. It's basically the reason why I bought the Zotac at the time, hoping that the problem wouldn't follow. ;(

    grub.cfg is only needed (and used) on EFI32 systems. Check /proc/cmdline after boot if your parameters are included.

    On N4000 usually EFI64 (or legacy boot) is implemented. Configuration file is /syslinux.cfg.

    On the AMD you can even use the amdgpu driver with:

    Code
    radeon.cik_support=0 amdgpu.cik_support=1 radeon.si_support=0 amdgpu.si_support=1

    How can I check /proc/cmdline in LibreELEC? It's not in the System Information page, annoyingly.

    That means I'll have to re-find the kernel parameters I've since deleted and test them again...