Yes, a RAM bottleneck can affect a GPU's performance.
Yes, a RAM bottleneck can affect a GPU's performance.
Dual channel setup... DDR3 1600 offers about 25.6GB/sec in dual mode, roughly doubling the rate or you can run manual tests and see around 51GB/sec. Note: I've observed similar speeds (though much higher latency) with my single 4GB DDR3 1333 stick compared to the 4GB dual channel DDR2 1066 5-6-6-18 configuration.
I just mentioned what I said. DDR3 1600 with dual channels delivers about 25.6GB per second, which is double the frequency (DDR3 3200-my next goal) or you can run the manual calculations (https://en.wikipedia.org/wiki/Memory_bandwidth) and reach around 51GB per second. Yes, DDR3 can achieve that speed as long as the IMC can support it.
Only when you find a kit with poor timing will you see the difference. For instance, dual channel DDR2 800 4-4-4-12 performs worse than DDR2 1066 5-6-6-18 in terms of latency. You can locate low-latency options for all types of RAM. I mentioned that bandwidth is influenced by the IMC, which will be categorized differently between the CPU and North Bridge. Even if my 4790K ends up with a bad IMC (though it might actually run at 4.8GHz safely with stable voltages), the heat output could still be a problem.