The Intel website seems to indicate it was just an earlier stepping of the ICH (I/O controller hub).
See page 2 of the following link (the paragraph entitled Customer Impact of change and recommended action):
<A HREF="http://developer.intel.com/design/pcn/Chipsets/D0000965.pdf" target="_new">Intel Discontinuance notice re: 810L</A>
<i>It's always the one thing you never suspected.</i>