Intel E8400 Specs
I run my E8400 at 4Ghz myself, on air. While on the net I'm crunching at 100% cpu usage. If I'm not crunching I'd be gaming. Unless I'm mistaken the max vcore for the E8400 according to intel is 1.45 I put mine at 1.3275 in the bios, and vdroop from the mobo drops it to lower than 1.2 at load.
Intel E8400 Desktop
E8400 Intel Processor Specs
1 Benchmark results were obtained prior to implementation of recent software patches and firmware updates intended to address exploits referred to as 'Spectre' and 'Meltdown'. Implementation of these updates may make these results inapplicable to your device or system. Software and workloads used in performance tests may have been optimized for performance only on Intel® microprocessors. Performance tests, such as SYSmark* and MobileMark*, are measured using specific computer systems, components, software, operations, and functions. Any change to any of those factors may cause the results to vary.