ISA-386C © 1989 Asus
The ISA-386C is a full-featured 386DX motherboard that became a staple for PC system integrators in the early 1990s. It was designed to support the Intel 80386DX processor (at 25, 33, or 40 MHz) and was built around a high-performance SiS (Silicon Integrated Systems) 85C310/85C311 chipset. The board is known for its "clean" Baby AT layout, which became the design language for almost all subsequent ASUS boards for the next five years. It supports up to 32 MB of RAM using 30-pin SIMMs and features a dedicated L2 cache subsystem (64 KB or 128 KB) that was highly efficient for the time.
The C Designation: In ASUS nomenclature at the time, the C suffix generally denoted a "Cache" or Compact iteration of their design. The ISA-386C solidified the idea that ASUS would provide the "best-in-class" implementation of the SiS chipset, often outperforming the reference designs provided by SiS themselves.
The AMD 386DX-40 Pairing: This board was the most popular partner for the AMD Am386DX-40 processor. The combination of the ISA-386C’s optimized cache timings and the Am386’s 40 MHz clock speed was considered the "performance king" of the 386 era, often matching or beating the performance of entry-level 486SX systems.