ref GA-X58A-OC - http://www.gigabyte.us/products/product-page.aspx?pid=3... "6 x 1.5V DDR3 DIMM sockets supporting up to 24 GB of system memory
* Due to Windows 32-bit operating system limitation, when more than 4 GB of physical memory is installed, the actual memory size displayed will be less than 4 GB.
3/Dual channel memory architecture
Support for DDR3 2200/1333/1066/800 MHz memory modules
Support for non-ECC memory modules
Support for Extreme Memory Profile (XMP) memory modules"
C1 is detection of ECC RAM.
Oddly, the Gigabyte GA-X58A-OC does support Xeon CPU's but there's no ECC listed support. Furher, the only '16GB/stick' is RDIMM which is not supported - period. IF Gigabyte made an error listing only 'non-ECC' then only UDIMM (unbuffered) would be supported -- if ECC is supported. Clearly, unless you have a Xeon CPU then forget any type of ECC RAM; none of the i7's (Gulftown or Bloomfield) support ECC.
Contact Gigabyte to see IF ANY ECC is supported, or exchange RAM for non-ECC and you can use up to 6x8GB (48GB) but for now that's it.