ATC-1425B © 199? A-Trend
The ATC-1425B was a mainstream 486-era motherboard designed to provide a bridge to the PCI bus. Unlike the high-end server boards you have already documented, this was a retail-focused "white-box" board. It is frequently discussed by enthusiasts because it is a "mixed bag"—it offered modern PCI slots but often suffered from performance bottlenecks compared to competing chipsets like those from UMC or Intel.
Chipset: SiS 496 (Northbridge) / SiS 497 (Southbridge).
CPU Support: Socket 3 (supports 486SX, DX, DX2, DX4, and 5x86 processors like the AMD Am5x86-P75). It natively supports both 5V and 3.3V processors.
Expansion: Typically features 3 PCI slots and 4 ISA slots (or similar configurations depending on the PCB revision).
Memory: Typically uses 72-pin SIMM sockets (FPM DRAM).
Form Factor: Baby AT, designed to fit into standard desktop and tower cases of the era.
The "Performance Mystery": The ATC-1425B is infamous in the retro community (specifically on VOGONS) for its abysmal performance scores. Benchmark testing often shows it underperforming compared to boards with UMC chipsets. This is largely attributed to the SiS 496/497 chipset implementation, which was notoriously conservative with memory wait states.
The PCI Divider: A notable feature of this board is the ability to manually set a PCI bus divider. This was critical for users attempting to "overclock" their 486 system by pushing the FSB to 50 MHz—without the divider, the PCI bus would run out of spec and cause system instability.
Missing Features: Unlike some of your "Pro" or "Corporate" boards (like the NCR or AMI Enterprise series), the ATC-1425B was often sold "barebones"—frequently lacking onboard PS/2 mouse headers or onboard IDE/Floppy headers, forcing users to rely on separate I/O cards.