How many interrupts is too many interrupts?

[marccenter]

Quick question for this thread, does a single quadrature encoder count as one irq or 2 irq's ? My quick calculations show that a wheel speed of 8 feet/sec with a 256 pulse/rev encoder yields about 1000 interrupts per second or is it really 2000 interrupts per second because the encoder has two channels? The addition of a second encoder can now push the processor to 2000/4000 interrupts per second. So, if 2 irq's per encoder, the processor will be operating nearly 4000 interrupts per second?