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I just found some DDR4 memory modules having shorter pins on left and right halves. enter image description here
I saw it by chance in a Kingston datasheet. And when I looked at two DDR4 Kingston modules next to me I saw it too.
Seems to be on all Kingston DDR4 memory modules. I didn't find other manufacturers doing it, but I haven't searched for long.

At first I thought this was to prevent electrical damage in case someone inserted/extracted a memory module while the motherboard is switched on. But seems not to be a rational idea because the modules are often inserted/extracted at an angle, letting the middle and one end to be electrically connected to the motherboard nearly exactly as if the pins were equal. Moreover, this is not only the pins, but the epoxy too. So maybe for a future form factor? The difference is small and may not be efficient as keyed connector.

Does anyone know what is it for?
Does only Kingston do this?

  • I've seen similar things on lots of types of connectors, and I've generally assumed it has to do with the pins you want engaging first, namely the grounding pins, or at least the pins that can ground. But, I don't know for certain. Check out SATA connectors to see more of these uneven pins. – music2myear Jan 10 '17 at 1:00
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This is to help with insertion. From www.kingston.com:

"Curved edge DDR4 modules feature a curved edge to help with insertion and alleviate stress on the PCB during memory installation."

enter image description here

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