Two other older AMD CPUs could be similarly unlocked:
- AMD K6-2+ with 128K of L2 cache can be converted to a K6-3+ with 512K. The CPU has a heatspreader that can be carefully removed revealing a series of zero-ohm resistors, moving it to the right location unlocks the cache. The CPU is still bound by binning as to whether or not it can be overclocked well.
- AMD Athlon XP could be overclocked with the "pencil mod", using a pencil to draw a conductive trace between two pads on top of the CPU, no delidding required.
It is, but pick-and-place robots like to work with zero ohm resistors compared to small pieces of wire. Also makes it easier to change later, you just swap reels.
In a sense that's correct, but "jumper" suggests these are deliberately components you can change whereas "Zero ohm resistor" is likely intended to be permanent.
In PCB manufacturing, a jumper wire is just a wire soldered between two points. A designer might or might not install jumper pins like those you refer to.
Regarding the use of a 0-ohm resistor instead of a jumper wire: wires are rather annoying to deal with in pick-and-place machines, while a 0-ohm jumper can be reel-loaded like any other part.
Or it might not work at all (as was the case for mine when I tried it).
There definitely was a period where AMD was shipping three-core Phenom IIs with a functional fourth core (demand was higher for the three-core SKUs than their actual defect rate appeared to allow), but I don’t know how plentiful fully-functional one’s actually were. And it was never guaranteed.
There was also the original Athlon, where there was an unjoined connection on top of the die. You could fill in the connection with a pencil and overclock the chip.
