Bought a new RAM stick to expand my desktop, didn't expect mysterious screen artifacts

Background

My current setup is an i5-8400 with 16G of RAM (two ADATA 8G 2400 sticks)

Then in daily use, 16G of RAM was already stretched thin. Whether for Android development or backend development, every compile was painfully laggy

It happened to be Double 11, so I figured I'd buy a 16G stick to expand, making a 32G dual-channel setup.

Looked around on JD, 2400 16G RAM was basically extinct, so I could only go with 2666. I figured the motherboard would automatically downclock 2666 to 2400, so it shouldn't be a big deal~

Then I picked up some no-name domestic RAM at a dirt-cheap price~

The Start

Bam, just like that, super fast

JD delivery arrived the next day. Gotta give that speed a thumbs-up~

A quick unboxing

Opened the packaging, pretty bare-bones~

The heat spreader is decent though

Installed it right away to try it out

Only when installing did I realize I'd been seating the RAM in the wrong slots all along

The B360M motherboard only supports dual channel and has four RAM slots, 1234; 12 is channel A, 34 is channel B. I'd previously put both sticks in slots 12. What a waste~

Just plugged the new stick into slot 3 and powered on!

Great, it POSTed on the first try

Ran a score test with Entertainment Master

Huge improvement~

The RAM score literally doubled

CPU and GPU scores also went up quite a bit

Looks like dual channel really does make a decent difference for performance

Checked and found all 3 sticks were at 2666mhz

Did it automatically overclock them for me??

Whatever, as long as it works. Overclocking 2400 to 2666 shouldn't be a problem, right?

Things Go Wrong

Just when I thought I could comfortably keep using it like this

The problems showed up

Straight-up blue screen + artifacts

Got a bit nervous. First reaction was that the new RAM was defective

Because I'd run into this kind of thing before—adding RAM and then getting artifacts

Opened the case like a pro, pulled out the new stick

Went back to the original two sticks, worked fine

OK, I was going to request a return, and that would've been the end of it.

However...

Tinkering

Since I'd discovered the original two 8G sticks weren't connected in dual-channel mode

That was definitely not acceptable

After pulling the new RAM, I immediately moved the original sticks from slots 12 to slots 13, to form dual channel

Turned out it wouldn't boot

I was shocked. Had the earlier automatic overclock to 2666 fried the old RAM??

Doesn't seem likely though. RAM doesn't break that easily

So I tried them one stick at a time

Found that each of these sticks worked fine on its own

Then I gradually paired them two by two, tried it, and they all POSTed normally

So first I put the original ADATA 8G heat-spreader stick + the newly bought 16G in dual channel, ran it for half an hour to test. Checked the frequency, still 2666, and sure enough, artifacts showed up in less than half an hour

At this point I could confirm it was a frequency issue. Went into BIOS, manually set the RAM frequency to 2400, installed all three sticks, POSTed normally. After booting I found the frequency had become 2133. Worked fine.

But 2133 performance is just too weak

Went into BIOS again and enabled XMP

XMP stands for Intel Extreme Memory Profile. It is a memory certification standard launched by Intel in September 2007. It applies to DDR3 and the latest DDR4. Intel claims it can "let you overclock RAM and compatible DDR3/DDR4 memory."

Before XMP technology appeared, RAM overclocking was already widespread. The demand first came from gamers, who were really living the Olympic spirit, demanding faster and stronger, so they could better wreck others in online games. To that end, memory manufacturers produced all kinds of gaming RAM that could run above their default frequencies. But back then these sticks had relatively poor compatibility, and gamers had to repeatedly tweak various timings in the BIOS to run games stably. Motherboard compatibility was also a big problem—it might work on this board, but not necessarily on one from another brand.

Intel sensed this market demand and launched the XMP memory certification standard in September 2007. The principle is that it extends two groups of profiles on the SPD.

(SPD is on every DIMM, a small storage chip (EEPROM), which records in detail many parameters including CL-tRCD-tRP-tRAS-CMD and so on, as well as manufacturer codes, etc. This is also why the BIOS can tell what kind of RAM we installed.)

The first profile group is generally the rated frequency speed, i.e. the speed the high-frequency stick's packaging guarantees it can reach. The second group is generally a higher extreme frequency.

Memory manufacturers are responsible for verifying the compatibility of these two profile groups with different chipsets, and submitting the RAM and those settings to Intel for testing. After testing, Intel grants XMP certification and publishes it on the official website (reference 1).

Its working principle is very simple and direct. The BIOS memory initialization program is responsible for reading that XMP data block from the SPD, and setting various parameters according to its requirements rather than the results of training.

Rebooted, frequency went back to 2400. Thought I was finally in the clear, but I was still being naive

Used it for a little while, artifacts again

This time it finally clicked

These two sets of RAM really weren't very compatible

Took the machine apart again, removed the two old sticks, left only the one new 16G stick

This time it was much more stable. Used it for two hours, until my App compiled a new version for release, all perfectly normal...

Recap

Although I still haven't fully figured out what the problem is

I've more or less pieced most of it together

First, the new no-name RAM should be fine

Second, the two old sticks should also be fine

As for why the artifacts happened, the motherboard/CPU probably has relatively high requirements for dual-channel RAM, generally needing sticks from the same batch with the same ICs

That also explains why even my two old sticks dropped to 2133 when running in dual channel

Forcing XMP on and pulling it up to 2400 doesn't help—it only makes the system unstable

---

(Caught Double 11)

So in the end I ordered another no-name 16G stick

These two old 8G sticks, I might consider selling them off~

Finally

Booted up at noon today and found

My Windows system is toast

Luckily I'm dual-booting, still have Ubuntu

Went into Ubuntu and checked—the files on the Windows drive were all fine

So weird, no idea where the problem is

I'll try to fix it tonight~

PS: GPUs are still expensive this Double 11. I'm out