I'd look at HWMonitor and monitor clock speeds across the 6 cores, the CPU should be capable of running about 3.8 GHz across all 6 cores for 30-60 seconds, and, if default Intel's 65W TDP is observed by the BIOS, clock speeds will decrease to closer to 2.9 -3.1 GHz... (Some mainboards may allow overriding the 65W TDP limit, effectively running the CPU closer to 95W at about 3.8 GHz sustained. If your cooling is better than Intel's stock cooling, which was known to be marginal for 8400 and 9400 CPUs, the boost duration time limits and TDP constraints can often be overridden within Intel's XTU application)
If you see clock speeds as low as 800 MHz, that could indicate either thermal throttling (which should only happen at 100C or above)...