Seeking mainboard recommendations (RE: Only half of RAM)

[blu-Z8efaSeK1ezqlBn2x/YWAg at public.gmane.org (Edward Ned Harvey)]

> From: discuss-bounces-mNDKBlG2WHs at public.gmane.org [mailto:discuss-bounces-mNDKBlG2WHs at public.gmane.org] On Behalf
> Of Rich Braun
> 
> - If I put a single 4GB RAM module in the machine, it sees 4GB.
> - If I put two 4GB modules into slots 1 & 3, BIOS reports 8GB but
>   Linux (64-bit) sees only 4GB.
> - If I move the modules to slots 1 & 2, BIOS and Linux both see
>   8GB (single-channel).
> - If I put 3 or 4 4GB modules into any combination of slots,
>   BIOS reports correct amount but Linux always reports 8GB.

By any chance, do you have a single processor in a two-socket motherboard?