Is it dangerous to insert (potentially) burnt RAM into a motherboard?

I recently wanted to add some RAM to my old computer, but unfortunately I mixed together "good" RAM with chips that I extracted from a computer that failed after getting too much voltage. I know it sounds like a bad idea to just plug it into a motherboard, so I figured I'd ask first - is there usually any protection in the motherboards against this kind of faulty chips? Also, how likely is that RAM got damaged when computer got his deadly current or failed for internal reasons (something shorted because of dust, failed components etc.)?

Solution 1:

This happened to me too recently. Faulty PSU provided 12V to the 5V standby line. The motherboard was killed. Magic smoke escaped through the cherry-red crater on one VRM IC.

The DDR4 module survived.

This shows that RAM can stands incidents that are deadly to the motherboard and possibly CPU. Not all of them, though. In my case it was the standby power line that was overvolted, not one of the main lines.

Even if the RAM module was damaged, it would be unlikely to damage the motherboard or other components. RAM voltage is generated by the motherboard itself using a dedicated converter. This converter should detect a short circuit in RAM and cut its power before any damage is done.

If you want to be a bit more certain, you can measure resistances of module's power pins using a multimeter. Look for pinouts/datasheet of a module similar to yours. These differ between different DDR versions (DDR3, DDR4 etc.) and DIMM/SO-DIMM (desktop/laptop) variants, but not between manufacturers. Also, DDR3L will have pinout identical as DDR3.

Once you have the pinout, find out which pins are connected to ground (GND) and which are power pins (Vcc, Vdd etc.). There will be a lot of these. They will be slightly longer than other ones too.

Figuring out which pin on the module is number 1 can be tricky:

• Try to match pattern of longer pins to GND/V pins in module's datasheet.
• Keep in mind that front side of the module contains only odd pins and back side contains even pins.
• The branding isn't necessarily on the front side of the module.
• Pin 1 is the first pin on the front side counting from the left, but pin 2 is the last one on the back side - they're neighbours on opposite sides of the module.

Use a multimeter to measure resistance between all V pins and some GND pins. If it's not zero, the module should be good. Resistance between GND pins will be zero, it's normal. Same between some V pins. Only resistance between GND and V is relevant.

Solution 2:

Your playing with fire here...I personally would not install this RAM.

But if your convinced that the cost of a new motherboard is worth the test...then just install the bad ram and see what happens when the system is started...leave the known good ram out until you've validated the bad ram.

Once you got the system running with the bad ram, do some performance testing on that ram, using something like this.