SY-4SAW2 © 1995 Soyo
The SY-4SAW2 is a highly regarded late-generation 80486 Baby AT motherboard engineered by SOYO Computer Industrial around 1995 to 1996. Built around a robust 168-pin Socket 3 layout, the board is powered by the legendary SiS 85C496 (Northbridge) and SiS 85C497 (Southbridge) PCI core logic chipset. It features native, widespread support for a wide array of 486 architectures, including Intel 486SX/DX/DX2/DX4, AMD Am486, and Cyrix chips, running on Front-Side Bus speeds from 25 MHz up to 50 MHz. The expansion subsystem layout provides four 32-bit PCI slots and four 16-bit ISA slots. Peripheral handling is fully integrated via an onboard SiS Multi-I/O controller hosting dual Enhanced IDE channels (supporting PIO Mode 4), dual serial interfaces, and a parallel port. System memory is routed through four 72-pin SIMM sockets supporting up to 64 MB of RAM, coupled with a highly scalable L2 write-back static cache (SRAM) DIP bank expandable up to 512 KB.
The PCI Bus Master Implementation: Thanks to the native SiS 496/497 chipset setup, the SY-4SAW2 bypassed the chaotic performance limits and physical length bottlenecks of the older VESA Local Bus standard. The board was famous for its excellent PCI Bus Mastering execution, allowing retro-builders to seamlessly install early PCI network adapters, high-speed graphics accelerators (like the S3 Trio or early Matrox cards), and custom sound cards without running out of stable bus bandwidth.
Silkscreen Clarity: SOYO motherboards of this era were widely praised by independent computer repair technicians and enthusiasts because the PCB featured comprehensive, clear silkscreened block diagrams and text guidelines printed directly next to the voltage and clock jumper banks. This completely removed the risk of frying a low-voltage 3.3V AMD DX4 or Am5x86 processor by accidentally running it at old-style 5V levels.