I'm doing a simple children's workshop in which they will build a small musical instrument on a breadboard with an attiny13a, ldr and a led. Right now it's powered by a 9v block and a regulator. Through some of the uncarefulness of the children, I discovered that the attiny13a seems to run just fine on 9v and the sound output is even louder! The regulator on the other hand gets hot, burning some children's fingers and is easily broken when the children wire it up incorrectly.
I've been running a test of skipping the regulator and running the 9v directly into the attiny13a. This has been running for more then an hour without problem, it doesn't get warm at all, though the clock speed might have changed a bit, which is no problem for my purpose. As long as the chip keeps running for the duration of the workshop (an hour) plus some more. Even though it seems practical to just run on 9v, the attiny13a -is- only rated for up to 5.5v. What could be some unexpected side effects?