FU340 © 1991 Abit
The FU340 is a high-performance 386DX motherboard that became legendary among retro-enthusiasts for its exceptional memory and cache performance. It is built around the C&T (Chips & Technologies) PEAK/DM chipset. While many 386 boards of the era were notoriously "picky" about cache configurations, the FU340 was engineered to handle larger L2 cache pools and faster RAM timings, effectively squeezing the absolute maximum theoretical performance out of the 386DX architecture.
Chipset: Chips & Technologies (C&T) PEAK/DM.
Processor Support: Socket 1 (80386DX at 25/33/40 MHz).
Cache: Supports up to 256 KB of L2 cache, but with a specific requirement for high-speed TAG RAM chips (notably the 64Kx4 configuration in U14/U15).
Expansion: Standard 16-bit ISA slots (with one 8-bit hybrid compatibility).
Memory: Utilizes 30-pin SIMMs, known for its ability to handle 32 MB+ of RAM with high stability, a feat many contemporary boards failed to achieve.
The Cache "Quirk": The FU340 is famous—and occasionally infamous—among collectors for its specific cache implementation. When pushing the board to 256 KB L2 cache, it deviates from the standard "32Kx8" TAG RAM usage found on most other 486/386 boards, requiring two "64Kx4" chips instead. This often trips up modern users who try to populate the board using standard "spares."
The "386 Performance Ceiling": Retro-benchmarking communities (like VOGONS) frequently use the FU340 as the control board for testing various 386 CPUs and coprocessors (like the Cyrix FasMath). It is widely regarded as having one of the "tightest" memory controllers of the 386 era.