We never[*] enable pen mode, so its effect on battery life is a non-factor here
.
[*] KFMon does send its screen updates in pen mode on the Elipsa to sidestep a host of issues with collision handling and rotation in the sunxi display driver (and only on the Elipsa, because the Sage driver was... let's go with "fixed" (but not really, it's just broken in different ways ;p)). That's only for the very short span of that update, and as such it doesn't warrant spinning up extra cores.
----
Technical sidebar about it, which doesn't concern us because of the above, but is mildly hilarious because sunxi:
Yes, it will utterly murder your battery: it pegs a CPU core to 100%, which requires Nickel to spin up the other 2 to 3 extra cores to deal with whatever it needs to deal with (which is also obviously a bigger load than usual, both because the pen is very chatty so keeping up with it on a very basic level is more straining, and because of actually doing pen stuff). What I call pen mode, which is only the display driver part of things, is only enabled on pen down, though.
And since we only support the pen as a touch input device and not a drawing tool, that explains why we never have to deal with pen mode
.
----
So, yeah, while the issues are less impactful to standard workflows, I cannot honestly say that the Sage/Elipsa are flawless. They're a mess, but, thankfully, it's just a mess that doesn't happen to trigger random crashes
.
(And it hasn't stopped me from using both of 'em as my daily drivers, as I find the battery issue hilarious on a technical level, especially compared to a Kindle PW5, but a non-issue in practice. And, as said above, despite being terribad, the display driver mostly "works", and most of what I'm talking about will never be noticed by anyone unless they're as obsessed about EPD as I am. And it doesn't randomly crash in standard workflows, so, eh, I'll take it
).