386 motherboard with a FOREX FRX46C402/FRX36C300/SIS85C206 chipset © 199? Unknown
These motherboards were typically mid-range solutions that utilized a multi-chip approach to handle the 386DX processor's memory and bus operations. The FRX46C402 served as a primary system controller, while the SIS85C206 acted as a peripheral controller (integrating standard PC/AT functions like the DMA, interrupt controller, and timers).
Cache: These boards typically featured support for 64KB or 128KB of "Write-Thru" L2 cache.
Form Factor: Most motherboards using this logic were manufactured in the Baby AT form factor, which was the standard for the 386/486 transition era.
BIOS: Systems using this chipset often have specific BIOS ID strings that include "FORX" or "FOREX," which are useful for identifying these boards in the wild. If you are refurbishing such a board, note that they are prone to battery leakage damage, as the barrel battery was often placed near the primary chipset logic.
Market Position: FOREX (often stylized as Forex) was a smaller chipset vendor compared to industry giants like Chips & Technologies or OPTi. Their boards are frequently found in "white box" or OEM systems from the early 90s, often catering to budget-conscious users who wanted the performance of a 386DX at a lower price point.