Serial Presence Detect (SPD) is a standardized way to automatically access information about a memory module.
Memory generally comes with conservative timing recommendations in the SPD ROM, to ensure basic functionality on all systems.
No Timings are specified for SPD speed, but who buys DDR3 2133MHz memory to run at 1600MHz?
F3-2133C11Q-32GAR
http://www.gskill.com/en/product/f3-2133c11q-32garSPECIFICATIONS TAB
Memory Type DDR3
Capacity 32GB (8GBx4)
Multi-Channel Kit Dual/Quad Channel Kit
Tested Speed 2133MHz
Tested Latency 11-13-13-31-2N
Tested Voltage 1.50v
Registered/Unbuffered Unbuffered
Error Checking Non-ECC
SPD Speed 1600MHz
SPD Voltage 1.50v
Fan lncluded No
Height 33 mm / 1.30 inch
Warranty Lifetime
Features Intel XMP (Extreme Memory Profile) Ready