Comment 18 for bug 1299857

http://www.realtek.com.tw/products/productsview.aspx?langid=1&pfid=31&level=5&conn=4&prodid=59

take a look at the datasheet for thowe AC97 registers

0:64 = 0808
0:66 = 0808
0:68 = 0a0a
0:6a = 8000
0:6c = 0000
0:6e = 0017
0:70 = c5a0
0:72 = 00c0
0:74 = 8388
0:76 = 8a90
0:78 = 1c8f
0:7a = 20d2
0:7c = 414c
0:7e = 4790