While we can discuss how it differs that will not fix the issue or allow such to be interchanged. So the differences are physical, and electrical.
You didn't reveal if the physical or packages were the issue so I'll note that in the electrical areas we have speed, organization and the all important SPD chip. There is a chip in the classic Intel design that manages the memory and those differ in what they support.
To go any deeper than this would have us pulling up Intel memory controller PDFs and more. Hope this sums it up for you.
Bob
I have one each of these venerable dinosaurs, and am surprised to find that contra general info, the RAM sticks are not interchangable.
They look the same, then you see that the slot between the connecting pins is in a different position. I need more GX260 RAM, so how does the RAM terminology differ between the two types?

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