Are you sure that there are no other sound chips there? It looks to me like the CS4231a is just a codec chip.
The CS4231a is a newer/upgraded chip compared to the CS4231 and CS4238
Looking through google images, I see it paired with:
Opti 924, 925, 929, 930
MAD16
Mozart
Aztech AZT2316R, AZT1605
Edit: Have you tried installing the plain Windows Sound System drivers?
Also, see this thread.. looks like it can be paired with basically whatever:
Microsoft Windows Sound System standard support in DOS games
EDIT 2: Here is information about and the files for the CS4231 DOS/Windows drivers
These are the installation instructions for The DOS/Windows drivers:
http://greyghost.mooo.com/pccbbs/commercial_d … top/qd2t00a.txt
DOS 6.2, 7.0
Microsoft Windows 3.1, 3.11
You can browse the folder by taking away the .txt file
http://greyghost.mooo.com/pccbbs/commercial_desktop/
The OS/2 driver package (cryst211.zip) mentions the Windows driver file names.
Windows drivers seem to be disk images which I haven't tried extracting... Crystal1.exe and Crystal2.exe which I have attached to this post.
The attachment crystal1.exe is no longer available
The attachment crystal2.exe is no longer available
These are for the CS4231, but maybe they will work for the CS4231a.
EDIT 3: And here is a set of DOS/Win3.1/Win95/98 drivers for the CS4231a
http://www.soundcard-drivers.com/drivers/66/66506.htm
The attachment cs4231a.zip is no longer available