alsamixer tells me my model is Nvidia MCP77/78 HDMI. On Ubuntu 11.04 with a 2.6.38-11-generic kernel (which includes the Alsa 10.0.18rc3 driver), I have to specify the model in /etc/modprobe.d/alsa-base.conf:
options snd-hda-intel model=dell-3stack
I have tested against model=auto and model=3stack, but this option has the best output quality on the internal laptop speakers. For information, the underlying audio codec is called STAC9227, this is what you need to find the possible options in ALSA’s documentation.