Question "Improve memory compatibility" in BIOS updates

[Assaf Patishi]

Hi everyone,
When they "Improve memory compatibility" does that actually mean that they are loosening the sub-timings so the motherboard could run more memory modules? So it actually makes performance worse?
Or maybe there are other techniques to improve the RAM compatibility. I can't think of another way to do it other than loosen the sub timings.
If this is indeed the case than it is not such a good thing to update the BIOS after all
But I am no great expert. I want to hear what other, more educated enthusiasts than me has to say about this.

 

[USAFRet]

Hi everyone,
When they "Improve memory compatibility" does that actually mean that they are loosening the sub-timings so the motherboard could run more memory modules? So it actually makes performance worse?
Or maybe there are other techniques to improve the RAM compatibility. I can't think of another way to "improve memory compatibility" other than loosen the sub timings.
If this is indeed the case than it is not such a good thing to update the BIOS after all
But I am no great expert. I want to hear what other, more educated enthusiasts than me has to say about this.

There is no single thing that falls under "improve".
Different manufacturers may do different things.

 

[Assaf Patishi]

There is no single thing that falls under "improve".
Different manufacturers may do different things.

Can you please elaborate?
Except from messing with sub timings, what kind of other methods exist?

 

[drea.drechsler]

Can you please elaborate?
Except from messing with sub timings, what kind of other methods exist?

When a system boots to a new memory module the CPU has to calibrate it's MCU to that memory, a process collectively called training. It's a complicated process, not just settling in on safe default timings defined in BIOS. Things like calibration of the data line impedances and voltage references are tested. It's pretty complicated and any number of those things can be changed to help it train more/different memory modules as they come to market. Even changes in the memory training process itself could improve compatibility.

DDR4 SDRAM - Initialization, Training and Calibration - systemverilog.io

A detailed tutorial on DDR4 SDRAM Initialization, Training and Calibration. Exploring topics such as Read/Write Training, ZQ Calibration, Vref Training, Read Centering, Write Centering, Write Leveling and Periodic Calibration.

www.systemverilog.io

 

[USAFRet]

Can you please elaborate?
Except from messing with sub timings, what kind of other methods exist?

There isn't a universal definition of "improve memory compatibility".

 

[Assaf Patishi]

When a system boots to a new memory module the CPU has to calibrate it's MCU to that memory, a process collectively called training. It's a complicated process, not just settling in on safe default timings defined in BIOS. Things like calibration of the data line impedances and voltage references are tested. It's pretty complicated and any number of those things can be changed to help it train more/different memory modules as they come to market. Even changes in the memory training process itself could improve compatibility.

DDR4 SDRAM - Initialization, Training and Calibration - systemverilog.io

A detailed tutorial on DDR4 SDRAM Initialization, Training and Calibration. Exploring topics such as Read/Write Training, ZQ Calibration, Vref Training, Read Centering, Write Centering, Write Leveling and Periodic Calibration.

www.systemverilog.io

Interesting, thank you.
So that means that it doesn't necessarily worsen the performance? I would like to believe that manufacturers won't make performance worse in trade for more stability.

 

[dangle1]

I would like to believe that manufacturers won't make performance worse in trade for more stability.

I would be cautious if you are contemplating a BIOS update based on the phrase "improves memory compatibility" on a system where the memory is already working well. Doubly so if reverting to the previous BIOS version would be difficult.

I have seen stability issues with related memory errors that reproducibly appear and disappear with BIOS upgrades and downgrades. It seems that BIOS updates that are intended to improve memory compatibility can sometimes significantly degrade performance with memory kits that previously tested fine.

 

[drea.drechsler]

Interesting, thank you.
So that means that it doesn't necessarily worsen the performance? I would like to believe that manufacturers won't make performance worse in trade for more stability.

I don't believe it should change performance, especially with respect to timings. That's because after training and once the system is in a state where it can boot with the memory it loads and uses the default timings stored in the memory module's SPD. Furthermore, you can change to using the module's XMP or EXPO settings (also stored in SPD) so then it's using those.

Most of the "improve compatibility" changes I've personally experienced improved the memory training process. In default settings memory is dogging it anyway with timings much looser than necessary for the low default clocks. Only when setting XMP does it start to shine, with faster clocks and tighter timings. And only when pushing the clock higher than XMP, while leaving XMP timings unchanged, does it show it's true worth. And of course, the full measure of value in any memory kit is only displayed at higher clocks when timings are tweaked to get lowest latencies. Which, BTW, is usually too minor to be actually appreciated anyway, except in specific benchmarks.

 

[Assaf Patishi]

I don't believe it should change performance, especially with respect to timings. That's because after training and once the system is in a state where it can boot with the memory it loads and uses the default timings stored in the memory module.

But aren't sub-timings motherboard specific? Different motherboard can set different sub-timings to the same memory kit. At least that's what I know.

 

[drea.drechsler]

But aren't sub-timings motherboard specific? Different motherboard can set different sub-timings to the same memory kit. At least that's what I know.

The kit I moved from my B450 to my B550 board had very similar default sub-timings but I can't be certain that's universally the case. At any rate subtimings have very little effect on performance, mainly on stability. That being the case, if you're tweaking your memory kit to within an inch of it's life it may matter for keeping it stable at a serious overclock with tight primary timings. But then you're going to over-rule pre-sets anyway so again, it just doesn't matter.

 

[Assaf Patishi]

thank you everyone for their input. This was a nice discussion.
But at the end I am still regretting I updated the bios, because I was always belonged to the school of thought that it's better to leave it alone if all working properly, and bios updates can even degrade performance in some cases.
I just thought that the bios update would fix a little issue I had, but it turns out that this is an intentional behavior of the motherboard and not a bug.. So I just updated the bios for nothing..

For some of you it may seem strange that I feel bad because of a little bios update, but I am actually thinking of getting another motherboard just because of this.
See..for me, a new motherboard, when it comes out of the box it is "perfect". And now I have ruined its perfectness by updating the bios. Yeah... I am that sick