Even when "idle", the comparators update things 2 blocks in front of it and 1 block behind it.
It seems to be doing it every redstone tick(i think) (2 gameticks) which can cause unecessary lag and problems because dispensers can fire on updates etc.
If you flick the lever in the picture the piston will extend because its being updated by the comparator.
Ok, so i actually checked through the code.
Apparently, the comparator is updating itself + the blocks infront/behind when it gets updated. um, derp? ๐
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This behavior is very useful. If it is unintended, it would be nice if this behavior was officially added in some other mechanism.
Because my issue was marked as a duplicate of this issue, despite being different, I'm going to put in a request here as well that it be considered a different bug. My issue is basically the same, except it happens behind the comparator as well. This means comparators are useless for checking dispensers because they cause the dispenser to fire rapidly each time they receive any redstone power. My bug only occurs in the latest snapshot (13w03a) and it actually interferes with gameplay, unlike this bug, which is an annoyance at best.
"Ok, so i actually checked through the code. Apparently, the comparator is updating itself + the blocks infront/behind when it gets updated."
Wow, that actually explains MC-7771
I mean, if update queue is lost after chunk unload, that is.
In 13w07a, directly pointing a comparator on normal mode at a self-resetting BUD causes the BUD to blink. Setting the comparator to subtract mode stops the pulsing.
Confirmed in 13w02b.