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An Intel 486DX microprocessor with itsfloating-point unit disconnected. All 486SX chips werefabricated with FPUs. If testing showed that the CPU was OKbut the FPU was defective, the FPU's power and bus connectionswere destroyed with a laser and the chip was sold cheaper asan SX, if the FPU worked it was sold as a DX.[Was this true of all 486SX chips?]Some systems, e.g. Aopen 486SX, allowed a DX to be pluggedinto an expansion socket. A board jumper would disable the SXwhich was hard to remove because it was surface mounted.Some SX chips only had a 16-bit wide external data bus. TheDX has a pin to select the data bus width (16 or 32). On thesmaller SX, that line is hard-wired to 16 inside thepackage. This is similar to the 286 SX, which was a 16-bitprocessor with an 8-bit external data bus.The Jargon File claimed that the SX was deliberatelydisabled crippleware. The German computer magazine, "c't",made this same theory the basis of an April Fools Joke.They claimed that if one drilled a hole of a specifieddiameter through the right point on a SX chip, this wouldbrake the circuit that disables the FPU. Some people actuallytried (and then bought themselves new processors).