how often is the $ea31 called interrupt c64?

On a Commodore 64, the default interrupt routine at $EA31 is called once per system interrupt, which is typically about 60 times per second on NTSC machines and 50 times per second on PAL machines. That means the routine is normally invoked on every vertical blank interrupt, not continuously.

What that means

• NTSC C64: about 60 calls per second.

• PAL C64: about 50 calls per second.

• $EA31 itself is the KERNAL interrupt routine entered from the IRQ vector, and it updates system time and related housekeeping.

Practical note

If you replace the IRQ handler on a C64, you usually still chain back to $EA31 so the clock, keyboard handling, and other system services keep working. The C64 docs also note that $FFEA is used by the routine at $EA31 to increment the real-time clock.

Simple version

So the short answer is: $EA31 is normally called once per interrupt, which is roughly 50 or 60 times per second depending on PAL or NTSC.