[geekmaster]

Okay, I opened up three SSH sessions on my K3. I ran htop in one. Then I ran gmplay with the Howard Lloyd clock video. Htop reported gmplay using 88% CPU. Then I ran tones, which made gmplay get jerky (slower framerate) and dropped gmplay to about 37% CPU, while tones took 40% CPU.

After about 20 seconds, tones aborted with "Write error: Input/output error", then gmplay jumped back up to 88%. I think a lot of that time is spent in system calls (especially on the K3, which does not return from the eink update until complete). gmplay spends a significant amount of time sleeping on the K4 or K5 (while the K3 is inside the system calls). Perhaps the K3 eink drivers use a wait loop or spinlock, consuming CPU overhead.