All this talk made me want to build a system around one of these rare gems. I found a processor for 80 quid (it isn't cheap), but used Z97 motherboard prices are through the roof! Oh man.
I
ALMOST did the same, but I already have at least half a dozen 'backlogged' parts-on-hand retro builds. I didn't need another.
Admittedly, the eDRAM-Broadwell is a 'curio' worthy of owning (and a gap in my collection). However, both its performance and 'place'
(Win8.1-10) is modern enough that I feel my main Zen 3 machine 'covers it'.
While '
not the same, at all, actually',
conceptually Zen3DVcache took up the mantle of what eDRAM was accomplishing. I'm much more inclined to spend money on an AM4 5800X3D than a
curio from Intel.
As to looking for a board...
While not OCable, single-socket 'server'/'workstation' boards using C222, C224, C226 chipsets (if compatible) will be stable and long-lasting. Every once in awhile, you can find someone liquidating or retiring that kind of kit. In my experience, it's more common to 'find a deal' on retired server kit than anything ever marketed towards Enthusiasts/OCers/Gamers.
The other option (which are often neither stable or OCable) are 'China-source' motherboards using Z97 or H97 chipsets. They're often '(re)built' around eWaste PCHs, and have varying levels of features and functionality. They are usually much cheaper than 'enthusiast kit' on eBay, though.
On the CPU, I'm not sure if it's as unique as we think it is.
I suppose this could be incorrect or 'incorrect, in context' but at least according to wikipedia, most
Iris (Pro)-supporting Intel CPU products utilized eDRAM.
edit: see @Fouquin 's post, below mine.