Broadwell was essentially a die shrink to 14nm from the 22nm process Haswell used.
The most notable upgrade was made to the iGPU which we now know as Iris Pro Graphics 6200.
Plagued by limited availability and weak overclocking headroom, Broadwell was quickly overshadowed by Skylake.

Intel’s releases have been so underwhelming that they are still selling Haswell processors alongside Broadwell and Skylake.
Two years later, it may be time to say farewell.
Intel has officially unveiled Broadwell-E, which consists of four processors covering 6, 8 and 10-core configurations.
The key difference being the PCI Express lanes, which have been increased from 28 to 40.
For reasons unknown, the6950Xhas a$1,723MSRP yep, you read that right.
This is an absurd price to pay and is only further stressed by Intel’s own Xeon range.
This means it would be possible to build a 20-core/40-thread system for roughly the same price as the 6950X.
All Broadwell-E processors officially support up to DDR4-2400 memory in a quad-channel configuration.
This is a 13% boost over the Haswell-E processors' DDR4-2133 spec.
7-Zip can fully utilize the 6950X so we see a similar figure from both the 5960X and 6950X systems.