Does CPU mining become efficient as memory requirements increase? I am focusing on an anti scrypt coin called Vertcoin which increases it's N-factor at a set interval. On their main page on bitcointalk it states that CPU computation will make gains as N-factor (memory requirements) increase. Can anyone explain as to how this is possible if the memory requirements can reach to > 4gb
Currently, for a custom-built high-performance desktop, 16 GB of RAM (or even 32 GB) is typical, while one of the best GPUs, the AMD Radeon HD 7990, has 6 GB of GDDR5.

Suppose the memory requirements were raised to 4 GB. That means that each thread will require 4 GB, so a CPU can mine on 4 threads at a time (16 / 4 = 4), while a GPU can only mine on 1 thread at a time (6 / 4 = 1.5, with greatest integer part 1).

Contrast this to the current requirement of 2 MB. A CPU is bottlenecked by the maximum number of threads it can do (even the very best Intel Xeons are typically capped at 32 threads), while a GPU with just 2 GB could easily do 1000 threads at once.