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A couple of historical CPU mods similar to this:

- AMD K6-2+ can be converted to K6-3+ by moving a 0-ohm resistor under the IHS to unlock the full 256K of L2 cache only present on K6-3+ models. The CPUs were basically all the same and were binned into separate SKUs using the position of this resistor.

- AMD K7 (Athlon XP) can be similarly unlocked by bridging conductive pads on the chip using something as common a graphite pencil.

- Intel Pentium 3 Coppermine chips could be run on earlier Pentium 2 boards by using a slotket adapter with a modified socket. The socket could sometimes be further modified to support the signaling used by even later P3 Tualatin chips, allowing for Tualatin CPUs to run on 440BX chipsets which were never designed for them. Also needs a BIOS mod and sometimes a VRM replacement.

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If anybody else wonders why a 0-ohm resistor is a thing, apparently it is because it makes it possible to install a jumper on printed circuit boards with the same equipment that is used for normal resistors.

https://en.m.wikipedia.org/wiki/Zero-ohm_link

You put 0-ohms where you think you might at some point want to have something else there like a > 0 ohm resistor or an inductor (for EMI blocking for example), it's much easier to just reprogram the SMD robot than to make a new PCB.

That's accurate, but given the lack of words to the effect of "You can also put", it deserves the clarification that the most common something else is - as the parent suggested - a ∞-ohm resistor, either as a specific component or more commonly in the form of the absense of a component.

Resistor shaped wires are also a lot less dangerous than fuse shaped ones. In my experience.

It can serve multiple purposes. You can have 0 ohm resistors to serve as a bridge to run a trace below if you're running out of space.

You can have multiple resistor footprints and depending on where the 0 ohm is placed, different configurations are enabled.

You can use it to be able to isolate parts of the circuit after the fact, although solder jumpers are more common for that purpose

A "0-ohm resistor" could also be more clearly called a "conductor", but it's not, despite its electrical function.

I suppose it's because the mechanical function is more salient: it is a standard SMD part like other resistors, capacitors, LEDs, etc, not a conductor etched on the PCB.

Not a CPU mod because it was enabled by BIOS and motherboard but still perhaps the most legendary CPU ever for overclocking: Celeron 300A (1998). >50% was typical just by changing one setting.

I remember upgrading my ATI Radeon HD 6950 to a 6970 - it was just a simple firmware flash! Worked beautifully. The card did eventually die so it might not have been the best idea, but in the meantime it did mine enough Bitcoins to pay for itself.

I flashed my Radeon 9550 into a Radeon 9600 Pro. Bumping the core/memory clocks from 250/200 to 400/300 was a pretty decent upgrade, and there was still some overhead for overclocking (IIRC, I got it up to about 450MHz on the core).

I remember the AMD unlocks using just an advanced setting in the BIOs. My cheap ass got a quad core processor for the price of a dual core!

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