The i386SX variant

The i386SX variant
The Intel 80386SX processor of a Compaq Deskpro Computer

In 1988, Intel introduced the i386SX, a low cost version with a 16-bit data bus (although the CPU remained fully 32-bit internally) intended to simplify circuit board layout and reduce total cost, similar to how the 8088 (used in the original IBM PC) simplified designs, but hampered performance, compared to the 8086. Only 24 pins were connected to the address bus, therefore limiting addressing to 16 MB (similar to the 68000), but this was not a critical constraint at the time. Performance differences were due not only to differing databus-widths, but also to the performance-enhancing cache memories often employed on boards using the original chip.

The original i386 was subsequently renamed i386DX to avoid confusion, though this would rather cause confusion later when the DX in the name i486DX instead indicated floating-point capability. The i387SX was a compatible i387 part (i.e. with a 16-bit databus) available as an optional math-coprocessor. The 386SX was packaged in a surface-mount QFP, and sometimes offered in a socket to allow for an upgrade.

The i386SL variant
Intel i386 SL processor inside an Acer notebook

The i386SL was introduced as a power efficient version for laptop computers. The processor offered several power management options (e.g. SMM), as well as different "sleep" modes to conserve battery power. It also contained support for an external cache of 16 to 64 KB. The extra functions and circuit implementation techniques caused this variant to have over 3 times as many transistors as the i386DX. The i386SL was first available at 20 MHz clock speed , with the 25 MHz model later added.