Shuttle XPC slim DH370 mini-PC Review: A Compact Digital Signage Powerhouse

Driving Three 4K Displays - There is No Free Lunch

The unique feature of the Shuttle XPC slim DH370 is the ability of the system to drive three simultaneous 4Kp60 displays from the integrated GPU. This is particularly useful for digital signage purposes. However, if one were to purchase the DH370, expecting it to playback three different 4Kp60 video streams on three different 4K monitors, the person is in for some disappointment. In fact, I actually tried playing back three different 4K streams on the three monitors, and ended up with stuttering videos in all three.

In order to study this aspect further, I fired up DXVAChecker's benchmark section and benchmarked each video in our decode / rendering test set for playback at 3840x2160. The first iteration was done with one monitor connected, the second with two, and the final one with three 4Kp60 displays being driven by the iGPU.

Benchmarking the VP9 Profile 2 HDR Stream with DXVA Checker

The best-case playback frame rate obtained for each video in the three different display configurations is presented in the table below.

The above numbers indicate that playback with a single monitor is fine for all the codecs (ignoring the VP9.2 video, as DXVAChecker was not able to use the ff-vp9-d3d11va decoder for the benchmarking). However, once more monitors are added to the fray, the ability of the iGPU to decode and play back the video at the required frame rate comes into question.

To be clear, the iGPU does not seem to have the ability to decode three simultaneous 60fps streams for any of the tested codecs irrespective of the resolution - the best case appears to be 124 fps for the 576i H.264 stream in the single monitor mode. That said, decoding three simultaneous 24 fps streams for certain codecs or some legal combination based on the numbers in the above table seems to be possible.

Driving multiple displays from a discrete GPU is relatively simple. The GPU has its own RAM where the frame buffers can reside. The GTX 1650, with its 128-bit memory bus, has a 128GBps memory bandwidth number. Contrast that with the Coffee Lake desktop processors, which, in dual-channel mode, have less than 40GBps available for both the CPU and the GPU together. It is likely that driving three 4Kp60 displays can take up a significant chunk of the available bandwidth, resulting in the performance loss that we see above.

The takeaway is that the Shuttle XPC slim DH370 can drive three 4Kp60 displays simultaneously. However, users must be prepared for some performance loss in this process.