• PCI Latency Timer

This is in cycles, not ms or anything else. It is a timer which sets a time-chunk for each PCI device to do something. If you want low-latency and have major horsepower, turn this one down. For more latency, and less multitaskability, but probably better big-block throughput, turn this one up. Default is usually 64.

• Spread Spectrum

Spread Spectrum is a method of reducing the effects of electromagnetic interference (EMI) between components of a single machine. All of the systems on a modern motherboard give off high frequencies of EMI, and the EMI from one system (say, the CPU) can drive frequencies of another system (e.g., the PCI Express chipset) through the air, to higher speeds which are potentially very bad. Spread Spectrum prevents this by varying the frequencies; some motherboards have separate spread spectrum capabililty for CPU, PCI/PCI Express, and other areas. It is unclear how often the issue shows up. Reportedly, overclockers need to turn this entirely off, at least on the CPU side.