90s Memes

IRQs were for setting up interrupts (stands for interrupt request). The CPU supports arbitrary interrupts from other hardware installed on the PC (like a soundcard saying that its buffer has room or is almost empty) but needed to map them to IDs so that they could be handled by the correct driver/code and didn't try to handle that soundcard interrupt as if it was coming from the keyboard and treating it as a keypress.

DMA stands for direct memory access and is used for communication between devices and the system. You had to set it up so that it didn't overlap with other important memory, like another device's DMA region, or memory used by the game or kernel (which, at the time, weren't really seperate).

Both of these things are still present on today's PCs but just have better management and support for the edge cases that previously caused issues (like drivers can support sharing an IRQ with other devices and the OS can handle allocating DMA spaces).