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Nimohtar · ‎05-20-2021

Hello everyone.

I am having problem with my recently purchased Z490-F, hoping someone can give some ideas.

I Initially got my hands on Patriot PVS416G440C9K memory, and plugged them into A2 and B2 RAM slots per manual's suggestion.
They worked great, all I needed was XMP profile and they would run 4400MHz no sweat.

Then I got another PVS416G440C9K which arrived 2 days ago, naturally, I plugged them into A1 and B1, but then my computer would not POST.
Tried a few times, always ended up in safe mode.
So I then tested all the RAM sticks, 1 stick at a time with every RAM slot.
All 4 of them can run 4400MHz on A2 and B2, but on A1 and B1, it would only POST if I run the RAM under 3000MHz.

I tried different version of motherboard BIOS too, still the same behaviour.

Is the motherboard DOA or am I just doing something wrong??

Any suggestions are welcome.

bscool · ‎05-20-2021

z490 works best with 2 sticks. Going to 4 will run at quite a bit lower speeds. I am not familiar with the z490 f but I had a z490 Hero and it could run 2x16 @4266 but using 4x8 even 4000 was tough to get stable. 3600 was pretty easy with 4x8 so I am not surprised the z490-F could only do something like 3000-32000 with 4x8. Sounds about right to me.

Edit looking at Gskill ram config they show 4x8 3600c16-16-16 and 4000c17 as compatible with your MB. It could be bent CPU pins. I did run into that issue with my first z490 Hero and using one of the "alternate" slots it would cause issues. I fixed the issue by straightening the bent pin myself but I would not suggest it for most. It is not the easiest thing to do. This was a Amazon return MB I got for cheap when z490 first came out.

https://www.gskill.com/configurator?page=1&cls=1529635169&manufacturer=1524725352&chipset=1589508048...,

Silent_Scone · ‎05-20-2021

Hello, mixing memory kits is not advisable. Often feel like a broken record when saying this, but if not wanting to tune the memory it's best to buy a kit in the density you wish to use.

This is because memory vendors bin the kits in the density they are sold in. When combining kits you eat into the guardband put in place by the memory vendor to ensure the best chance of operation on a given board and CPU. Of course, these things are often a lottery regardless, but by doing so you run a risk that the modules will not work when combined at their rated frequency, timings and voltage.

All of the latter may need to be adjusted in order to pass POST stress tests and operating system stress tests as you have discovered.

13900KS / 8000 CAS36 / ROG APEX Z790 / ROG TUF RTX 4090

Nimohtar · ‎05-20-2021

Hi guys,

Thanks for your reply. I do understand that going to 4 sticks mean slower speed, even if they are the exact same model.
But I think I should clarify something.

What I meant is, even with only 1 stick of RAM, if plugged into A2, or B2, I can set it to 4400MHz and it would run without problem.
But if this single stick of RAM was plugged into A1 or B1, then it would only POST if the speed was set to below 3000MHz.
If I had all 4 sticks in, it would not POST unless it is running at 2133MHz.

bscool · ‎05-20-2021

Yeah I understood what you were saying.

I know on z390 I could run a single stick in any slot at roughly the same speed but z390 is daisy chain and z490 is t topology and works best with 2 sticks. So i would imagine you take a big hit in speed/stability when you run them in a1 or b1. I helped someone on another board that was having issues even getting xmp 3600 to work(z590 is t top like z490) and it was because he had them in a1 and b1. He could only run something like 3200 when in a1 and b1. He put then in the correct slots and xmp 3600 worked fine.

https://www.overclock.net/threads/help-appreciated-on-if-i-should-return-some-ram-for-my-10850k.1778...

Z490-F RAM Issue