EISA Enterprise-III © 199? AMI [American Megatrends, Inc.]
The Enterprise-III is a high-end 486-era server/workstation board that was designed when American Megatrends was still a major player in the "complete system board" market. It is a massive, highly complex PCB that features a unique mix of EISA (Extended Industry Standard Architecture) and VL-Bus (VESA Local Bus) slots, a configuration that was rare and highly sought after by users who wanted the bus-mastering capabilities of EISA with the high-speed graphics potential of VLB.
Chipset: AMI’s custom chipset logic, designed to manage the overhead of both VLB and EISA buses simultaneously.
CPU Support: Socket 3 (supporting 486SX, DX, and DX2 processors), with an additional non-ZIF socket for an 80487SX or OverDrive CPU.
Expansion: Eight total slots: 6 bus-mastering EISA slots and 2 fully buffered VL-Bus master slots.
Memory: 16x 30-pin SIMM sockets (supporting up to 256 MB of parity-checked FPM RAM).
L2 Cache: 256 KB (via discrete cache chips, often needing specific configuration).
Form Factor: Proprietary large-format "Server" AT, designed for massive tower cases.
The "Buffered" VLB: A unique feature of the Enterprise-III is its fully buffered VL-Bus implementation. VLB was notoriously unreliable when populated with multiple cards due to electrical loading on the CPU bus. AMI's design used active buffering to keep the load constant, making it one of the few VLB motherboards that could run reliably with a full set of expansion cards at 33 MHz.
The "ECU" Necessity: Like the Enterprise-IV, this board relies on the EISA Configuration Utility (ECU). You cannot simply plug-and-play cards; you must boot from a diskette, run the configuration utility, and provide the .cfg files for every EISA card installed, which the board then stores in its NVRAM.