386 motherboard using the Forex FRX46C402 + FRX46C411 + SiS 85C206 chipset © 199? Unknown
This motherboard is a "transitional" 386 platform. It was designed to support the 386DX processor but includes cache controller logic that allowed for significantly higher performance than standard ISA-based boards. Its rarity stems from the fact that Forex was a smaller chipset vendor, and their logic sets were often used in limited production runs by OEMs who were trying to keep costs lower than a C&T or OPTi-based system.
Chipset:
FRX46C402 & FRX46C411: The core logic pair that handles memory, CPU interface, and cache control.
SiS 85C206: The common "Southbridge" of the era, which integrated the keyboard controller, DMA, and interrupt controllers into a single chip.
CPU Support: Strictly 386DX. Enthusiasts often attempted to use TI486DLC upgrade processors in these boards, but historical reports indicate that the Forex chipset was famously finicky with these "486-in-a-386-socket" upgrades.
Expansion: Typically features standard 16-bit ISA slots. It is a "pure" ISA board, predating the widespread VLB or PCI transition.
Cache: Usually features 64KB or 128KB of L2 cache in DIP sockets.
The "Micro Express" Link: Many of these boards were found in systems sold by Micro Express. If you have a machine with this chipset that has a "ME" or "Micro Express" sticker on the back, it is likely using a customized BIOS version that is slightly more stable than the generic Forex reference designs.
BIOS ID String: Boards using this chipset often return the ID string 30-0400-ZZ1101-00101111-070791-FORX. If you see the "FORX" suffix, you have confirmed a Forex-native BIOS.