Please.
Physical transmission distances make up a very, very small fraction of overall latency. Its virtually all in signal processing, not the signal transmission.
You can beat on the I/O Controller for possibly increasing latency, but don't use propagation delay as the reason.
(Appreciable) Delays will be the result of the clock rate of the infinity fabric and the internal speed of the memory controller.
You have a transmission delay of around 1ns for every 15 cm travelled. So the extra latency added (due to transmission route lengths) from deviating from core, through an on-socket memory controller rather than directly from core-located memory controller will be measured in pico-seconds... if not femto-seconds.
Yeah, I can't understand why people keep bringing up the "distance" argument. I'm tired of refuting it constantl:
As I mentioned The Core 2 Duo had 800 MHz DDR2 with very similar transfer times to 3200 MHz DDR4, and can achieve
~65ns memory latency with a low 1066 MHz FSB.
Some really dumb MoBo schematics to get the point across:
On the Intel's motherboard (D975XBX) used in the review: The Memory Controller is on the 82975X Northbride chip just to the left of the socket.
So the red line represents the shortest path a hypothetical singal must travel - From the DIMM slots to the NB and from there onwards (via the
FSB running at a lowly 1 GHz) to the processor.
Now look at the distance covered on a B450 motherboard:
The CPU is certainly closer than the Northbridge of old. And then from the IO chiplet the CPU Chiplet, you could measure it in millimeters (not centimeters as is the case with the northbridge).
Not only Zen 1 already has the Infinity Fabric clock-speed at 1.6 GHz in case of 3200MHz RAM. It will probably be higher with Zen 2 (as they mentioned they have substantially refined it).
Let me repeat that: Core 2 Has shown AIDA latencies between 60-70ns with memory with similar (actually a bit worse) transfer times to DDR4 3200MHz
CL16 . ZEN 1 in comparison, can't really do that, not without much tighter timings.
Yet ... Hurr Durr ... AMD can't possibly improve the Latency with Zen2, if it's a chiplet designe. It's impossible due to "distance"!
TL;DR:
As Atari already mentioned. The whole distance argument is flawed from the start. Signal Processing is the bottleneck, not Transmission distances.