I have X8DTI-F motherboard. I have read the manual.
Configuration:
2x E5620 CPU
6x 16GB Quad Rank Memory (3x 16GB per CPU)
Currently, it runs at 1066 MHz
What happens if I add 2 more 16GB DIMMs to it – there by populating 8x 16GB – will it downclock to 800 or still run at 1066?
It will Run at 800 MHz, you can see below
http://www.supermicro.com/support/resources/memory/X8_DP_DIMM_population.pdf
due to speed limitation