HOW MEMORY BANDWIDTH IS KILLING AMD’S 32-CORE THREADRIPPER PERFORMANCE
AMD’s 32-core Threadripper 2990WX is the fastest consumer CPU ever sold. And let’s be clear: We’re in full agreement with anyone who said that. But we would also be the first ones to say it has its limitations, too.
The most glaring is the lack of consumer applications that can truly exploit the cores available. The other limitation is apparent in the diagram below, which shows how AMD built this 32-core monster. Rather than a single chip with every single CPU core on it, AMD connects four dies using its high-speed Infinity Fabric.
WHY MEMORY BANDWIDTH AFFECTS THE 32-CORE THREADRIPPER
If you look closer at the diagram, you can see that two of the dies don’t have their own memory controllers or PCIe access. Instead, they have to talk to an adjacent CPU die.
It is, essentially, like having a two-apartment unit where the second one must access the hallway outside by going through the first apartment.
Perhaps more important is the overall bandwidth available. AMD had initially said the total bandwidth available between the four CPU dies was 25GBps bi-directional. The company amended its original documentation to state it was total bandwidth. Compare that with the 16-core Threadripper 2950X, with its
