Latencies like this are doable with a lot of tuning on Intel CPUs; out of the box you'll get to the 40s with fast memory. And those CPUs have three cache levels instead of two...
A good old-fashioned 2010-era gaming PC would already get down to around 50 ns levels.
It's definitely really good, but considering it's rather fast RAM (DDR4 4266 CL16) and doesn't have L3 it's not that surprising.
I've written a benchmark to measure such thins and from what I can tell.
Each fast core has a L1D of 128KB.
The fast cores have a cluster with 12MB, cache misses to to main memory.
The slow cores have a 4MB L2.
The cache misses from the fast L2 can't quite saturate the main memory systems (I believe it's 8 channels of 16 bits). So when all cores are busy you keep 12MB of L2 for fast, 4MB of L2 for the slow cores, and end up getting better throughput from the memory system since you are keeping all 8 channels busy.
Not just 128 bits wide (standard on high end laptops and most desktops), but 8 channels. The latency is halved and over the last decades I've only been seeing very modest improvements in latency to main memory on the order of 3-5% a year.
A good old-fashioned 2010-era gaming PC would already get down to around 50 ns levels.
It's definitely really good, but considering it's rather fast RAM (DDR4 4266 CL16) and doesn't have L3 it's not that surprising.