Random screen blackout and i915.powersave=0

I have been experiencing random screen blackout on my dinosaur machine.  I googled the internet and found some suggestions to add "i915.powersave=0" to a line in the /etc/default/grub file.

While I am still watching if it works, it seems that adding this to the grub slows down the browser (at least slightly).

What does this "i915.powersave=0" do?

Thanks in advance.