Which component houses the I/O cards in the System 6000?

The correct choice, which identifies the component that houses the I/O cards in the System 6000, is the mainframe. The mainframe serves as the central structure of the System 6000, accommodating not only the I/O cards but also providing the necessary connectivity and functionalities that integrate all system components.

I/O cards are crucial as they facilitate the input and output of audio signals, thus playing a key role in the processing capabilities of the system. The mainframe is designed to efficiently house these cards, ensuring optimal performance and reliability.

In contrast, the remote CPU primarily manages signal processing and other computational tasks, but does not serve as a housing for I/O cards. The TC Icon functions as a user interface for controlling the system but does not contain any electronic components like I/O cards. Lastly, while a power supply is essential for providing energy to the entire system, it does not serve as a housing unit for the I/O cards within the System 6000. Overall, the mainframe is specifically designed to support and integrate the necessary components, including the I/O cards, making it the correct answer.