Hi folks. I have never seen a guide that compared 1333 vs 1600 RAM as well as various size configurations in a Macbook Pro. I wrote one up. It's online here, but I've pasted the gist here if you don't want to click away. Pictures and tables are included in the web link if you really wanna get into the nitty gritty. Background Some quick internet searching told me that later model Macbook Pros could, in fact, handle 16GB of memory (despite Apple saying 8GB is the limit) and can run DD3 Memory at 1600 MHz (despite Apple saying 1333 MHz is the limit). So, I ordered 2x8GB of Corsair Vengeance PC1600 notebook memory at $57.99 a piece. Tack on a $10 NewEgg discount, and the grand total was $104.98. Only $1.50 more per GB than I paid to upgrade my machine from 4GB to 8GB in December 2011. For whatever reason, it was cheaper to order 2 single 8GB sticks ($115.98 before discount) than the dual-pack of the same memory ($119.99). You can download the data used in this analysis. Test Machine Late 2011, 17″ Macbook Pro with quad-core 2.5GHz Sandy Bridge i7 CPU. Benchmark Software Geekbench 2.3.1 for Mac OS X x86 (64-bit) Test Configurations 4GB (1x4GB) 1333MHz, Corsair (CMSO8GX3M2A1333C9) 4GB (2x2GB) 1333MHz, Samsung (Stock Apple memory) 8GB (1x8GB) 1600MHz, Corsair Vengeance (CMSX8GX3M1A1600C10) 8GB (2x4GB) 1333MHz, Samsung (Stock Apple memory) 16GB (2x8GB) 1600MHz, Corsair Vengeance (CMSX8GX3M1A1600C10) Procedure I ran Geekbench 64-bit for the Mac 5 times on each of the above configurations to account for random error. (Admittedly, on configuration 3 I forgot to record one of the results and couldn’t be bothered to re-install the memory, so n=4 for configuration 3.) While Geekbench gives about 20 different numbers, I recorded 5: the overall composite and the four summary statistics: Integer Performance, Floating Point Performance, Memory Performance, and Streaming Memory Performance. Analysis More memory improves Geekbench overall scores: about 1.5% increase from 4GB to 8GB and 1.2% increase from 8GB to 16GB Dual channel makes a big difference. All dual channel configurations outperform the single channel configurations: 20-30% for Memory performance and 35% for Stream Memory performance. Dual channel configurations with more memory do better than dual channel configurations with less memory on the order of 3% for Memory performance and 8% for Stream Memory performance More memory improves floating point performance marginally. The 16GB configurations has slightly more variance between measures on memory related tests and slightly less variance on processor related tests. Theoretically, that means more memory equals more consistent processing performance relative to lower capacity configurations and slightly less consistent memory performance relative to lower capacity configurations. This probably has absolutely no real world or practical meaning, but the claim stands up to scrutiny in statistics class. Conclusions Do not run in single channel mode. It’s inefficient. One can expect a similar percentage increase in benchmarks when moving from 4GB to 8GB as from 8GB to 16GB. That is to say, there are diminishing returns as memory increases in size, but there are returns nonetheless. Unsurprisingly, increasing memory improves memory benchmarks more than processor benchmarks, but there is a small improvement on the processing front. Cautions I cannot get a good handle on 1333 vs 1600 performance on synthetic benchmarks because I have to compare dual channel to single channel performance. Nevertheless, other benchmarks suggest you may notice a slight speed boost on very intensive work, but moving from 1333 to 1600 is not going to make any noticeable difference for regular human beings. Get the 1600 RAM to feel good for being on the bleeding edge, and then laugh at yourself for the absurdity of it all. The cost difference is marginal, in any event. These benchmarks are for a late 2011 i7 quad core. Results may, of course, vary, but I suspect these types of changes will remain relatively consistent from Mac to Mac. I do not know how far back one can go and still run the memory at 1600 MHz, however. Final Thought Benchmarks aside, 16GB feels faster than 8GB and 8GB feels faster than 4GB. This is especially noticeable when many applications are running. The upgrade is worth it for the cost.