AMD Ryzen memory optimisation - The effect of tRC timings
Published: 14th July 2017 | Source: OC3D Internal testing | Price: |
tRC Timings - A Discovery
With AGESA version 18.104.22.168, AMD Ryzen users are able to adjust a lot more memory settings than before, giving us the option to change the tRC timings of our memory.
Ryzen and Stock tRC Timings
When looking at several different DDR4 memory kits at varying speeds, we found one common thing that for Ryzen's stock tRC timing, with the value changing depending on memory speed but offering the same real-time value of around 0.047 microseconds.
This means that tRC will have much more room for improvement with higher speed memory, where stock tRC timings are highest, with our G.Skill Trident Z memory allowing this timing to drop to 48 at 3200MHz. This is an improvement of 36% for this specific timing.
The important thing to note here is that your memory kit's rated (XMP) tRC timings are not being used here, but they are defined by your motherboard. These tRC timings are used by every Ryzen motherboard that we have tested so far, leaving room for optimisation.
|Memory Clock Speed||Actual Clock Speed||Stock tRC Timing||Time passed per memory clock (Nano Seconds)||Time passed for tRC (Micro Seconds)|
Finding out what your tRC Timing XMP value
First users should find out what their memory tRC timings should be, which can be commonly found using CPU-Z. tRC is typically the values of tRP (RAS# Precharge) and tRAS added together, which is this case is 48 (14+34) for our G.Skill Trident Z kit. This is found for this memory on the XMP-3200 section of the memory's timings table.
This means that we are planning to reduce the tRC time from 75 to 48 in the BIOS, which is a 36% reduction, which should increase your system memory performance in certain scenarios.
It is important to note that tRC should not be lower than tRP + tRAS for stability reasons, though you can use speeds that are higher than this if required.
Alternatively, you can check your memory's XMP table on other application, or inside your BIOS on select motherboards.