Intel 80486SX

The Intel 80486SX is an [Intel 486DX]? microprocessor with its [floating-point unit]? (FPU) disconnected. All 486SX chips were fabricated with FPUs. If testing showed that the [central processing unit]? was OK but the FPU was defective, the FPU's power and bus connections were destroyed with a laser and the chip was sold cheaper as an SX; if the FPU worked it was sold as a DX.

This needs to be confirmed. --STG

Some systems allowed a DX to be plugged into an expansion socket. A board jumper would disable the SX which was hard to remove because it was surface mounted.

Some SX chips only had a 16-bit wide external data bus. The DX has a pin to select the data bus width (16 or 32). On the smaller SX, that line is hard-wired to 16 inside the package.

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Based on material from FOLDOC, used with permission.