I recently bought an HP Stream 8 (Tablet with quad-core Atom and Win 8.1) and thought this would be the perfect way to play some old RPGs on the train. I've downloaded GOG Galaxy and installed a few old games (Darksun, Darksun 2, Albion, Battle Isle) and tried to play them. Nothing happens, when I click on the "Play" button.

I think, the tablet should be strong enough for these games? (It plays ToME on Steam.) Are there any settings I'm missing or does DOSBox just not run on Atom cpus?

It's certainly not the CPU. I would suspect something about the configuration...

1) Did you check that DirectX was installed ?
2) Did you try running the programs as administrator ?
3) did you try launching the game directly, not through Galaxy ?

Yeah, as someone who has run DOSBox games on an Acer Aspire One D257 equipped with an Intel Atom N570 under Windows 7 Starter, Windows 10 Home, Debian 7 "Wheezy" and Debian 8 "Jessie" since about 2011, I can probably say with some amount of confidence that DOSBox runs well enough with the Atom processors.

Only issue might come out of using the "Dynamic" core, as Atom cpu's don't (didn't? maybe it has changed with newer models?) do KVM virtualization. I've never had any issues, so the dynamic core might not actually use KVM, but that might be a question for Qbix or one of the other DOSBox developers.

I don't have much experience with Windows tablets, but the display may not be able to switch to the resolution dosbox wants to use. Try changing one of the games to windowed just to see if it'll start.

Well, did you make sure the config files included a line mounting the SD card as the drive where the games are supposed to be installed ?

something like this :

mount C [the full path of the game directory on the sd card]
c:

Plug in a mouse.

Try opening the config file and changing the output to something else:

Try overlay, ddraw or opengl

Default is surface but can have problems with some devices

I'd day Direct Draw first, then OpenGL.

As for the tablet having DirectX11... The whole move to 11/12 really breaks compatibility since they don't support the older API's. From what i can tell DirectX 9 and earlier are faster, but lack newer features. Sorta the comparison between COD and say Unreal or Quake. I thought Unreal and Quake were phenomenal graphics wise. Maybe i'm just concentrating more on the 'Fun' part and less on the smoke effects, reflections, physics and other addons that they feel have to be there.

i'm gonna guess the gog settings of dosbox might be to pointing to the wrong location when you installed it to the SD card?

maybe you could try installing a separate copy of DOSBox in your HDD/SDD, and config it to run the dos executables from the SD card. that's as easy as drag and drop(drag the dos program onto DOSBox) for MOST games, but you could also use a GUI program or a bunch of batch files to automate it a bit.

DOSBox is an x86 application, the Atom CPUs are x86 processors, if they can run Windows they can run DOSBox - not a doubt about that.

For maximum chance of success while trying to run a computer program on a machine in toy-form (ie tablet): simplify the process, give up about this "cloud client this and client that" crap, run (and leave) DOSBox alone, check the emulator configuration.

Newer DirectX versions are bundled with widnows itself methinks. But for 9 you need to use this tool https://www.microsoft.com/en-us/download/details.aspx?id=34429