tRAS timing

[The red spirit]

Hello, I decided to mess with RAM a bit. I have been lowering primary timings to see how low I can go, but there is a mystery timing that I have no idea to how to set. It's tRAS. Many sites say to set it to 2xtCL+tRCD. Wikipedia says that it should be tCL+tRCD. That would seem straightforward, but it really isn't. My current tCL is 15, tRCD is 19. So at least tRAS would be 34, but I set it to 28 and it's perfectly stable. It remains stable in Memtest64 (TPU special) for hours, I notice no other obvious instability. It seems to work well. I tried 26, but it didn't boot. Anyway, I wonder how tRAS should be set. I wonder if my procedure of going as low as possible isn't exactly correct and if memory may experience very infrequent failures as results. I also tested my DDR3 system and it has CL10 and tRCD11, but it remains stable with tRAS set to 16. It may do less, but I haven't tested it so far. It seems that those RAM timing calculating rules just don't apply.

Note:
My tRCD and tRP are stock, at 19, because motherboard seemingly can't change their values. I try that, but CPU-Z reports that nothing has changed.

 

[BellaCiao]

No rule for tRAS Cas + RCD initiation phase to achieve stability, this may drop in some ICs, if you don't try 27, you have reached the limit of tRAS.
You can also try RCD and RP 18.

What they say starters are rules are meant to be broken, make your own rules