ALC665 is a High Definition (HD) Audio Codec IC from Realtek Semiconductor, used on older desktop motherboards with Intel and AMD chipsets. It supports standard onboard audio functions including speaker output, line-out/line-in, microphone input, and front-panel audio.
In repair work, a faulty ALC665 can cause no sound, missing audio device, distorted output, or mic issues. While clearly a legacy desktop codec, it still has occasional replacement demand for older office and home PCs.