Slow image rendering with display hardware acceleration

I have the previous generation of Mac Mini (2018: Intel UHD Graphics 630 1536 MB, 16Gb RAM, 3.2 GHz 6-Core Intel Core i7. Display is ViewSonic VP2785-4K.) and am suffering slow rendering with display hardware acceleration set to “auto” and was wondering whether this is expected. This occurs on both C1-21 and C1-22.

Changing the hardware acceleration settings reveals that it is the display acceleration that seems to be the problem. With display hardware acceleration set to “never” it does a partial rendering (that is with moving from the initial blurry state to nearly sharp) in less than a second, whereas in “auto” it takes between 2 and 6 seconds to do that. The setting of the processing hardware acceleration seems to make no difference. The processing is, then, 2 to 6 seconds faster overall before the spinning wheel stops spinning when display acceleration is set to “never”.

Though possibly a separate issue, there are occasional rendering artefacts (small black boxes or brightly coloured “X”s). These usually disappear on full rendering, but not always. I’ve rebuilt the OpenCL kernels, to no obvious effect.

Kommentare