From the ALSA wiki
See the ThinkPad600 page for the information about configuring the Alsa Sound drivers for the IBM ThinkPad600 Laptop... these notes may be valid for other thinkpads too. The IBM Bios Update Instructions say the Thinkpad Simple Boot flag must be disabled for the 600, 600E, 600X, 770, 770E, and 770ED. Also, I've seen mail in the linux-thinkpad mailing list that suggest even Thinkpads with CS46xx chips can use the cs4232/cs4236 drivers, though personally I'd try the CS46xx drivers first.
Links to Thinkpad websites:
These first two are great, pretty current (as of Jan 2003) pages. They talk about sound, but so much more as well. Check them out!
Thomas Hood's "Debian GNU/Linux on an IBM Thinkpad 600" webpage. Chock full of good things. He's tried everything! http://panopticon.csustan.edu/thood/tp600lnx.htm
Raph Levien's Linux Page. Especially see his info about the batteries. http://www.levien.com/tp600.html
The tpctl page: if you're sick of PS2.EXE under DOS, you want tcpctl. This page also discusses why pnpdump doesn't work, and bugs with lspnp and setpnp in older Linux 2.4 kernels. http://tpctl.sourceforge.net/tpctlhome.htm
The linux on a thinkpad mailing list (yes, at the top it says Thinkpad 770-- but it really has mail regarding any Thinkpad model). If you have a Linux Thinkpad problem you can't solve anywhere else, the answer is probably somewhere here. http://www.linux-thinkpad.org/bm/tp_mailing.html
The IBM support site, which has downloads (like PS2.EXE for configuring the sound system) and documentation. The Thinkpad 600 is model 2645-51U, the 600X is 2646-8EU. http://www.ibm.com/support/us/
Retrieved from "http://alsa.opensrc.org/ThinkPad"