I run one of my motherboards with only a four pin and its fine, but its four cores, not eight. Never heard of that brand of psu. You can buy an adaptor, but it still only uses the four wires. It just depends on how your motherboard was built. Should be okay though. You can't hurt anything.
switched mode power supply
The way members from India generally refer to a psu
SMPS is an awfully broad term to refer to the PSU though since SMPS refers to the voltage regulation principle in general that applies to everything from MW-class industrial/utility UPS and ubiquitous wall adapters to point-of-load regulators embedded in smartphones, bluetooth accessories, USB devices, etc.