After updating the BIOS on a Gigabyte GA-MA785GM-US2H (rev. 1.0) motherboard, I was able to unlock the second core on its Sempron 140 CPU [specs], metamorphosizing it into the fictional “Athlon II X2 4400e” CPU.
Strangely, the BIOS update tool from Gigabyte wouldn’t run on Windows 10; I had to spin up FreeDOS to flash it. (Apparently an outdated W10 Home edition build doesn’t even have 16-bit EXE support available…)
When the second core was enabled, the OS wouldn’t boot until I overclocked the vcore by about 0.1V, however. (And now it doesn’t seem to successfully shut down…) I would have messed with it further, but I don't know the first thing about overclocking—this being the first motherboard I’ve ever owned that supported it. (And, given how underpowered this CPU is compared to my other options, this is mostly an adventure in historical interest, anyway.)