Edgar:
If your system seems to work with the 512MB RAM, I wouldn't change it (unless you're determined to get rid of the UMB message, in which case I would try 2 pieces of 100 MHz/256MB memory).
Here are the specs for the 810E chipset north bridge(GMCH) from Intel's website:
"The GMCH provides the interconnect between the SDRAM and the rest of the system logic:
├в ┬в 421 Mini BGA
├в ┬в Integrated Graphics controller
├в ┬в 230 MHz RAMDAC
├в ┬в Support for Intel Celeron and Intel Pentium III processors with a 66, 100 or 133 MHz system bus.
├в ┬в 100 MHz SDRAM interface supporting 64 MB/256 MB/512 MB with 16Mb/64Mb/128Mb
SDRAM technology
├в ┬в Optional 100/133MHz 4 MB Display Cache
├в ┬в Downstream hub interface for access to the ICH
├в ┬в TV-Out/Flat Panel Display support"
Therefore, the chipset will support 512MB RAM but apparently at 100MHz. I think the references on HP's website may be for the product as originally released and hardware changes were later made without updating the docs, or it may have to do that the system can be configured in several ways. Keep in mind that 256MB memory very likely did not exist when these documents were created.
HTH
M
Make a great day!
Roger
