5820K and 5960X have hit nearly similar overclocks in recent memory - chips with 3.4 and 3.3 GHz all-core turbo had a majority of chips (~75-79%) going to 4.5 GHz. 4.5/3.3 = 36% overclock, which is quite high by modern standards.
Sandy Bridge and Sandy Bridge-E were fantastic overclockers too with many samples going to 4.7 GHz (even on HEDT!).
Broadwell-E, too, could hit some solid clocks if you were willing to push more voltage... a lot of people got later samples to 4.7 GHz despite the numbers being closer to 4.3 in SiliconLottery's tests. Probably an uncomfortable amount of voltage and heat, but, Broadwell itself wasn't as bad as people took it to be, just the prices, and the L4 cache on Broadwell-C limiting the core clocks.
https://en.wikipedia.org/wiki/List_of_Intel_Core_i7_processo...
https://siliconlottery.com/pages/statistics
This is somewhat of a function of Intel not really pushing clocks in those days. 3.3 GHz all-core turbo is nowhere near what the silicon could deliver - generally I would punch in 4.1 GHz all-core on my 5820K and that would be stable without any other (explicit) settings adjustments.
And that is a factor of the TDPs - in those days TDP on desktop was expected to cover your max boost under a (reasonably) worst-case load. It has been a thing for a long time in laptops, but the desktop market was different. AMD was actually the one who introduced the "boost TDP is higher than box TDP" concept (aka PPT) to the desktop market with Ryzen 1000 - and then Intel started following suit once they started ramping up core counts and clocks with the 8700K/9900K.
But 140W is actually plenty for a hexacore or even octocore running at 3.3 GHz and even under a worst-case load scenario... and 91W is plenty for a quad-core running at max turbo too. The numbers weren't as phony back then.
https://www.anandtech.com/show/10968/the-intel-core-i7-7700k...
https://www.anandtech.com/show/8426/the-intel-haswell-e-cpu-...