Dr. Stephan Pabst

When running "GTK3VICE-3.8-win64-r45310" (under Windows 11), the original issue is fixed and VICE now behaves exactly as the real C64 does. (That is, the game "Astro Chase" cracked by "Tankard", downloadable at "https://csdb.dk/release?id=66174", will now hang in the cracktro as soon as you press the space bar too long. Previous versions of VICE instead switched over to the gameplay after pausing for a few minutes.)

I have tried to build VICE locally (under Windows 11, for Windows) some time ago, but I was unable because the sound libraries were unavailable. But if you provide a pre-built version, I will be happy to test the original issue (intro of game "astro chase" cracked by "tankard" hangs on real C64, but only pauses for a few minutes with VICE).

... and my real C64 is the "classic" model - thus the corresponding VICE emulation behaves correctly.

CIA1 timer A IRQ triggers faster on VICE than on real C64

Just a wild guess... In the implementation of the CIA's interrupt functionality, there must be some mechanism saying "if an interrupt condition is fulfilled then set the IRQ line active but continue normal execution for at least 3 clock cycles before jumping to the interrupt handler". If the "but continue normal operation for at least 3 clock cycles" step does not take pending VIC IRQs into account, the resulting behaviour should be quite similar to what we are observing.

This incompatibility has been detected while running the game “Astro Chase”, cracked by Tankard: https://csdb.dk/release?id=66174 This game will hang on a real C64 if the space bar has been pressed too long in the intro (thereby causing a lightpen interrupt), while it starts correctly after having paused for several minutes with VICE.

For the sake of completeness: The issue is also reproducible with VICE 1.13 (under MS-DOS 6.22).

This incompatibility has been detected while running the game “Asteroids”, cracked by Tankard: https://csdb.dk/release?id=66174 This game will hang on a real C64 if the space bar has been pressed too long in the intro (thereby causing a lightpen interrupt), while it starts correctly after having paused for several minutes with VICE.