In 1988, Intel introduced the i386SX, a low cost version of the 80386 with a 16-bit data bus. The CPU remained fully 32-bit internally, but the 16-bit bus was intended to simplify circuit board layout and reduce total cost.[6] The 16-bit bus simplified designs but hampered performance. Only 24 pins were connected to the address bus, therefore limiting addressing to 16 MB,[7] but this was not a critical constraint at the time. Performance differences were due not only to differing databus-widths, but also to performance-enhancing cache memories often employed on boards using the original chip.
The original 80386 was subsequently renamed i386DX to avoid confusion. However, Intel subsequently used the 'DX' suffix to refer to the floating-point capability of the i486DX. The i387SX was an i387 part that was compatible with the i386SX (i.e. with a 16-bit databus). The 386SX was packaged in a surface-mount QFP, and sometimes offered in a socket to allow for an upgrade.
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