286 motherboard with Headland G2 chipset - MAME machine

Motherboard:

Octek DCS-286 © 198? Octek

A classic late-1980s Baby AT motherboard built around a high-performance Intel or AMD 80286 microprocessor running at 12 MHz or 16 MHz. It is defined by its reliance on the Headland G2 (GC101/GC102) core logic chipset, which dramatically reduced motherboard manufacturing costs by consolidating the entire IBM PC/AT peripheral controller logic, clock generation, DMA, and interrupt handling into a highly efficient two-chip solution. The DCS-286 layout features six 16-bit ISA expansion slots, two 8-bit ISA slots, a dedicated socket for an 80287 math co-processor, and dual-tier memory support combining old-style DIP sockets with modern 30-pin SIMM blocks.

TRIVIA
Hardware Shadow RAM: The Headland G2 chipset on this board features early hardware-level "Shadow RAM" capabilities. It allows the slow 8-bit or 16-bit ROM BIOS routines to be copied directly into fast system RAM during the boot sequence, drastically speeding up video BIOS calls and character rendering in text-heavy DOS applications.

The CMOS / Extended Setup Interlocking Bug: The customized 1988-dated American Megatrends Inc. (AMI) BIOS written for this board features a notorious architectural layout quirk closely tracked by modern hardware archivists. Modifying parameters inside the "Extended NEAT Register Setup" utility (such as bus wait-states, DMA clock scaling, or shadow RAM toggles) frequently corrupts and resets the standard variables (date, time, hard drive layout parameters) on the "Basic Setup" page, forcing retro-computing builders to carefully toggle setup bytes in a specific sequence to achieve a stable POST layout.

CONTRIBUTE
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