Addressing RAM - CDDA Challenges in DC Games

[CrisMod]

(07.11.2023 12:11)SWAT писал(а):  SQ mode in last versions can save at least 8 KB memory with IRQ, and 16 KB without IRQ.
But I'm not sure that memory is a issue for all these games. Most issues gives channel usage conflict between ISO loader and the game.

Hey @SWAT, it's great that you occasionally provide more insights into the functions, giving us a chance to have better control over the settings we adjust rather than going blindly. So, thanks for the tips.

For those who may not be familiar with these terms, I'll try to explain in simple terms (SWAT, feel free to correct me if I'm wrong):

1. Sound Queue (SQ): The Sound Queue is a mechanism that manages the order in which sounds are played or processed by an audio system. It functions like a queue where incoming sounds are organized and played one by one in the order they were added. This is useful to prevent audio overlaps or conflicts when multiple sounds need to be played simultaneously. These are essentially the audio packets that are queued in the limited RAM before being reintegrated into the same available RAM blocks once they're processed. These are the audio glitches that we hear and SQ could help on it because will keep ready the next package of datas.

2. Interrupt Request (IRQ): Interrupt Requests are signals sent by the Dreamcast's hardware to the IDE interface where you've installed your mods. If you have the MOD LED, you'll notice it behaves differently when these parameters are enabled (or disabled). The LED is an excellent MOD signal to give you an idea of the data bus frequency between the DC hardware and the IDE MOD, and also what's happening in the background. In simplified terms, it briefly interrupts the continuous requests you see when the CDDA is turned on. So, what SWAT means is that if you activate it, you allocate 8KB of RAM to add this feature, and if you deactivate it, you free up more RAM, making an additional 8KB (16KB) available for the presumed audio needed by the CDDA mechanism.

@SWAT, the issue I've noticed (with some quick testing) is that when you enable those 2 functions, for example "Racing Simulation 2," which has the least audio stutter compared to others – in other words, it's the game that might come closer to somewhat bearable audio when CDDA is enabled – the problem is that when you activate SQ or IRQ, these functions not only affect the audio part but also influence all the game's data buses that need to be reloaded into RAM on the next reload cycle. So, whatever settings are applied for Sound Queue and Interrupt Request, they also apply to the entire graphical aspect and create stutters throughout the game, with some risk of minor graphical artifacts in-game.