MSI BIOS Z390 -- Memory Performance vs tRTL/tIOL
Note.
This is just a personal summary and it does not represent MSI or Toppc
Figure 1. Advanced DRAM Configuration Parameter (XMP on)
We can tell from figure 1 that
RTL CHA/D1/R0 = 74
RTL CHB/D1/R0 = 74
IOL CHA/D1/R0 = 13
IOL CHB/D1/R0 = 11
RTL CHB/D1/R0 = 74
IOL CHA/D1/R0 = 13
IOL CHB/D1/R0 = 11
For many users, they would just change the values for all of them to attempt to improve memory performance. However, there is also another way of doing it.
Figure 2. Alternative Option for Modifying RTL/IOL Value
To begin with, what is RTL Init Value (CHA/CHB) & IOL Init Value (CHA/CHB)?
You can firstly imagine RTL/IOL as a necessary parameters for CPU to determine the best signal for memory training during boot process. In case you fix RTL/IOL values, sometimes if the surrounding condition changes such as temperature, CPU frequency, it is likely that you could encounter issue like the system only boot 9 out of 10 times or even worse.
So why do we want to “play” with RTL/IOL Init Value instead of the actual tRTL/tIOL values? The reason is that RTL/IOL Init value is the baseline for CPU to begin the memory training. The CPU will start fill up the actual tRTL/tIOL value based on the init values. If the signal ever goes too strong or weak, CPU can still slightly modify the actual tRTL/tIOL (range is usually +/- 1) so to avoid the occasional no boot condition.
Note that if you set the value too tight, your system can still experience boot failure.
In short, the pros of doing it via RTL/IOL Init value is that you can minimize the chance of memory training failure but the cons is that the tRTL/tIOL values could be slightly different during every boot.
Below is an example and just for your reference, I personally like to have +1 on RTL Init Value on CHB when using 4 DIMM motherboard and same RTL/IOL Value when using 2DIMM motherboard and that is just my habit. This value really depends on motherboard/memory.
Remember that if those values are too tight, your system could still fail to boot. This is only useful for the condition when you set a proper tRTL/tIOL value in BIOS, but “sometimes” you just can’t boot into the system.
Figure 3. Set RTL/IOL Init Value
Figure 4. New tRTL/tIOL value
Figure 5. Default XMP performance
Figure 6. XMP Performance (After applying new RTL/IOL)
Also, there should be plenty of users noticing that when XMP is enabled, MSI motherboard would overclock BCLK to 100.8.
In future BIOS update (about 2 to 3 weeks), MSI will
1. open an option for user to decide whether they want to enable the BCLK auto overclocking feature or not
2. open an option for user to optimize latency (when the function is enabled, system will try to improve the memory performance depending on the RAM quality) -- Figure 7
Figure 7. Round Trip Latency Optimize
MSI is hoping to provide a more intuitive/flexible way for end user who wants to overclock to play with their motherboard.