“AD1981B: AC'97 SoundMAX® Codec”
Looks like 3-metal planarized CMOS around the 350 - 500 nm node. Minimum observed M1 half-pitch in analog logic is 750 nm, digital may be smaller.
Size is approximately 2730 x 3140 μm (8.57 mm2)
Random analog logic
Random area of chip, focal plane on M3
Same area, focal plane on M1