+in bank 15, calling ROM routines or accessing hardware needs special code. The
+cc65 runtime implements wrappers for all functions in the kernal jump table.
+While this simplifies things, it should be noted that the wrappers do have
+quite an impact on performance: A cross-bank call has an extra 300µs
+penalty added by the wrapper.
+
+
+<sect1>Interrupts<p>
+
+Compiled programs contain an interrupt handler that runs in the program bank.
+This has several advantages, one of them being performance (see cross-bank
+call overhead mentioned above). However, this introduces one problem:
+Interrupts are lost while the CPU executes code in the kernal bank. As a
+result, the clock may go wrong; and (worse), serial interrupts may get lost.
+
+Since the cc65 runtime does only call the kernal for disk I/O, this means that
+a program should not do file I/O while it depends on interrupts.