Investigating the Performance Impact of Ryzen Infinity Fabric

With the release of AMD’s ‘Zen’ based Ryzen series of CPUs a very interesting side-effect has occurred in the PC marketplace. Namely what was once simply marketing spin has become a potential reality. You see a dirty little ‘secret’ of the PC industry is that RAM speed has very little impact on overall performance compared to putting that extra money towards a better CPU, GPU, SSD. So much so that for most consumers opting for anything much above what the CPU manufacturer designed the CPU around resulted in minor improvements. Oh sure synthetic benchmarks told a different story, but the net improvement for opting for uber-high performance, and uber-high priced, RAM is minor to say the least.

AMD’s Ryzen CPU series actually changes all that… and makes RAM speed possibly critically important. This is because AMD made a very interesting design decision and tied their Infinity Fabric speed to the RAM speed. Specifically the Infinity Fabric runs at 1:2 clock speeds of the RAM (or to be even more specific at 1:1 of the IMC’s speed setting as DDR4 is double data rate and ‘DDR4-2600’ is actually running at 1300mhz not 2600mhz as the name suggests). Since the Infinity Fabric is how the two CCX (4 core CPU Complex building block) talk to each other and the rest of the system the higher the transmission speed, the higher the bandwidth… and theoretically the higher the overall performance. This is because the shorter the period of time one block of CPU cores are waiting for data the happier they will be.

Today we are going to investigate exactly how big a deal this really is and what speed of RAM you should opt for… and put some of the savings over an Intel HEDT system towards. To do this we are going to use three different sets of 32GB (4x8GB) DDR4 RAM. Option 1 is going to HyperX Fury DDR4-2133 RAM (model HX421C14FB2K4/32), option 2 will be HyperX Fury DDR4-2400 (HX424C15FBK4/32), and the third is going to be HyperX Fury DDR4-2666 (HX426C15FBK4/32). We have chosen theses three sets of RAM as they are good value kits we have used in the past, offer great capacity, and look sexy as all get out.

Equally important all three sets of DDR4 RAM are 1.2v 4x8GB kits with good timings of C15 or better – so they are fast for their class but not so fast as to require much in the TLC department. Put another way these are low hassle, ‘plug and play’ kits that should just plain work while not skimping on capacity. As for prices, 32GB of HyperX Fury 2133 will set you back about $220 USD, the 2400 kit will cost you $250 USD, and the 2666 kit is still a very reasonable $290. While this is ‘only; a $70 variance across all three sets it is almost enough of a difference but a Crucial MX300 275GB drive which costs about $90 (USD).

We have stopped at DDR4-2666 as beyond this people have to choose between capacity and speed… and honestly anything above DDR4-2666 is a bit of a crapshoot when it comes to working with Ryzen processors and large capacity RAM sticks. So let’s warm up our kits, getting our Ryzen 1800X humming along… and see what the actual numbers are and if the added -albeit still very reasonable – expense is worth it or not.