The GameTank's audio system, referred to as the Audio Coprocessor or ACP, is a 65C02-based subcomputer that computes PCM samples and outputs them to a digital-to-analog-converter.

The ACP consists of a 65C02 processor, a 4K dual-ported RAM that is shared with the main system's memory map, a programmable timer that triggers the 65C02's IRQ at regular intervals, an 8-bit DAC, and a buffer register.

The 4K dual-ported RAM encompasses the entirety of the memory that the ACP can address. The memory range $0000-$0FFF maps to the RAM and address above that will cycle over that range.

The same memory can be accessed by the main system's processor between addresses $3000-$3FFF, utilizing the second port of the SRAM.