Alpha PCI 164-266/300 Design Guide

This document serves as a design guide for Digital's Alpha PCI 164-266/300 motherboard, intended for system designers embedding compute engines. It thoroughly describes the board's features, configuration, functional operation, and interfaces. The motherboard is built around the Alpha 21164 Microprocessor (available at 266 MHz or 300 MHz) and the DECchip 21171 core logic chipset, which includes the 21171-CA (CIA) control/I/O/address chip and 21171-BA (DSW) data switch chips.

Key features include a memory subsystem supporting 32MB to 512MB of DRAM via eight SIMM modules, and a configurable L3 backup cache (Bcache) that supports 2MB, 4MB, and 8MB sizes with various access times, set via onboard jumpers. The main I/O bus is PCI, operating at selectable speeds (25 MHz or 33 MHz), offering three dedicated PCI expansion slots (one 64-bit, two 32-bit) and one shared PCI/ISA slot. An integrated Intel 82378ZB Saturn-I/O (SIO) chip bridges the PCI and ISA buses, providing two dedicated ISA slots and a shared slot. Onboard ISA devices include a keyboard/mouse controller (Intel 8242), a combination chip (National 87312) handling IDE, diskette, dual serial ports (UARTs), and a parallel port, as well as a Time-of-Year (TOY) clock (Dallas DS1287).

Software support involves a 1MB flash ROM preloaded with a debug monitor and Windows NT ARC firmware, alongside initial boot code in a serial ROM (SROM). The guide also details system address mapping across various PCI and memory regions, power and environmental requirements (including a 116W power dissipation and cooling fan specifications), and the physical dimensions of the standard full-size PC AT board. Configuration parameters, such as CPU clock divisors and Bcache settings, are extensively documented through jumper settings.