While fixing some sound related issues in WEC Le Mans 24/Hot Chase HW, I’ve got across a code snippet that was stealing a lot of cycles in Hot Chase. Turned out that Master CPU was checking for an hand-shake bit from sound CPU after sending a sound command data and an irq request line, and looping to a pretty fat chunk of time until eventually timing out if the default state is ‘1’ (which was default behaviour so far).  Fixing that, and gameplay speed finally normalized for good.