Memory corruption when not using recommended slots

lightsaber · August 12, 2021

I think I've got my problem solved but would like some extra knowledge on why. I'm building 2 identical systems they have an intel 11600k, Asus prime z590-p motherboard and 2 x 16 GB G.Skill ripjaws V ddr4 3200mhz ram. So I didn't look through the manuals a whole lot and assumed dual channel would activate and be fine so long as you matched the ram slot in channels a and b. On the asus board its label a1,a2, b1,b2 assuming that labeling i figured go with slot 1 in both and I'd be golden. Computer boots fine installs windows everything seems great. Move on to building PC number 2 same story. But while loading drivers and software i get a blue screen with some video corruption. Usually a good sign that the video memory is borked and with onboard graphics somethings is wrong with the ram. but I figured I hadn't gotten the drivers fully installed yet so I'd press on. More crashes and some windows updates not downloading correctly made me realize the problem wasn't going away. So ran memtest 86 and it got to test 6 in the series before it showed errors but had it had a lot past that point. Tried 1 stick in a1 and then the other same issue. Well turns out the recommend configuration is a2, and b2 for 2 sticks. figured I had a bad slot on the motherboard so I'd try that anyway before I'd ran through the manual. No issues what so ever with that setup which is the recommendation. I do have xmp enabled but that didn't seem like it should be a big deal. The ram is rated for it and from what i understand the 11th gen series can handle 3200mhz just fine by default. I figured I'd try memtest on the first computer that I didn't think was having issues since i thought it was fine just to confirm and same story. It showed corruption later on in the test as well. All I can find is some people saying yeah that will happen if you don't use the recommend slots but does anyone know why? I'd like to have a logical reason to why it would cause a problem so i can make sure to remember and avoid it in the future. Is it just an xmp detection thing with voltages not set correctly in the wrong slot or does the memory controller just not like the second slot with out the first in the channel being populated. I guess I thought gone were the days of things like rdram that needed continuity blank sticks and special memory orders to keep things going. Any thoughts would be appreciated.

Bombastinator · August 12, 2021

Why you have to use a OR b rather than a1 and b1?

betting your first machine worked but it was only running 8gb

so why do you have to fill one channel before moving to the other. I know the ancient reason, but it will be different now because there’s so many ways people arrange that stuff. Possibly specific to that model. Generally it came down to cost vs speed. It used to be that if you didn’t completely fill the first channel bad things would happen. Then stuff happened so you could only half fill one slot. It cost more in engineering and manufacture but saved in customer service. This seems to be the break even point. They could probably do it so you could stick in any memory anywhere but it would be expensive and slow. I’ve seen single channel, dual channel triple channel and quad channel. Heard about 8 channel but I’ve never seen it.