Failing memtest on one set of ram, would same set work again?

[Kevint77]

Hi there. First off, I've used memtest for so long, and it's helped me immensely.
Thank you for creating such great software that you allow us to use, free. I appreciate it.

My first memory problem!

I'm on an i7 11700, with a z590 msi tomahawk.

I had my heart set on using 3600mhz, c16, dual ranked memory.

I originally purchased 8gb x 4 sticks of crucial ballistix, and with 4, I can't pass memtest while running a speed higher than 3444mhz. I then thought I'd try buying 16gb x2 crucial ballisix, because it's sometimes still being reported to be dual ranked. I bought 5 kits, all single ranked.

I then bought g skills rip jaw 3600mhz c16 16gb x2... they are dual ranked. This is what I wanted!

But it won't pass memtest. When I have both sticks installed into proper dimms, it fails memtest with over 100 errors every time. If I run memtest just using 1 of the sticks, both sticks fully pass memtest. I'm so confused.. if both sticks are fine, why won't they work together and pass?

I wanted to make sure my motherboard wasn't bad, so I ran a full night memtest on the 3600mhz 16gb x 2 crucial ballistix I bought, and it fully passed. (Wish these weren't single rank, they look so much nicer too).

So what gives here, why do both sticks pass individually, but fail when using 2 sticks?

Any help would be appreciated. I'd love to buy two new of the same sticks if they'd be likely to work.

Thanks

[David (PassMark)]

I don't have the numbers handy, but the performance difference between 3444Mhz RAM and 3600Mhz RAM is likely really tiny for most applications. (most apps are bottle necked by GPU, disk, network, single thread CPU performance, etc..).

It isn't that uncommon for two sticks to behave differently from 1 stick. Two sticks,
1) Allow dual channel mode, which changes access patterns a lot. Addresses are interleaved between the sticks.
2) Changes the memory map so some small areas of RAM that could not initially be tested (because UEFI BIOS locks them) now get tested.

[Kevint77]

I don't have the numbers handy, but the performance difference between 3444Mhz RAM and 3600Mhz RAM is likely really tiny for most applications. (most apps are bottle necked by GPU, disk, network, single thread CPU performance, etc..).

It isn't that uncommon for two sticks to behave differently from 1 stick. Two sticks,
1) Allow dual channel mode, which changes access patterns a lot. Addresses are interleaved between the sticks.
2) Changes the memory map so some small areas of RAM that could not initially be tested (because UEFI BIOS locks them) now get tested.

thanks for the reply David. I'm going to test the difference in 3444 vs 3600 and see if this problem is worth trying to continue to trouble shoot.
last night I ran 8gb x 4 of 3600mhz c16 ram on memtest over night, and it fully passed. The other times I tried it, it would randomly shut down my PC at times during the test. After it fully passed last night, I just tried starting memtest again, and it got through through first pass, and on the second pass it shut down my PC again.
any idea what could be going on there?

[Kevint77]

Just doing some additional research, this is oh the 8gb x 4 3600mhz c16 kit.

Using all 4 ram at 3600mhz causes random restarts, but has fully passed memtest once out of 4 attempts without restarts.
Using all 4 ram at 3444mhz isnt producing restarts and is passing memtest.


The optimal memory locations for my motherboard are in slot #2 and # 4.

If I use just 2 sticks, in 2 and 4, I can run at 3600mhz with no errors or restarts.

If I run with 2 sticks in slots 1 and 3, I can't even post any higher than 2666mhz.

[David (PassMark)]

I should point out all the above terminology is wrong

Your Crucial ballistix is likely DDR4-3600 RAM. Which means is only 1800Mhz clock speed.
While the 3600 value refers to 'mega-transfers' per second. The double date rate (DDR) design means two transfers occur per clock cycle. So transfers per second are double the clock speed. Sometimes, confusingly, it would also be referred to as PC4-28800 (where 28800 is the MB/sec data transfer rate).
But a huge number of PC stores & people are getting the terminology wrong.

According to Intel the i7-11700 CPU only supports up to DDR4-3200. So it is not very surprising you are having a problem getting them to run at DDR4-3600.