82346 SYSTEM CONTROLLER

The Intel 82346 System Controller is a highly configurable, software-controlled device designed for PC systems operating at speeds up to 33 MHz. It eliminates the need for hardware jumpers and defaults on reset to maintain IBM PC/AT compatibility, allowing systems to boot at the CPU's rated speed before BIOS configures it transparently to the user.

Key features and capabilities include:

• Memory Performance Optimization: Supports built-in page mode operation, two- or four-way DRAM interleaving, and fully programmable memory timing to maximize system performance with various DRAM types, including low-cost options.
• Advanced Refresh Management: Manages both system board and slot bus refresh (in conjunction with the 82344 ISA Bus Controller), offering coupled (synchronous) and decoupled (independent, programmable) refresh modes. This allows for slower refresh rates suitable for low-power, slow-refresh DRAMs, with refreshes staggered to minimize power supply loading.
• Flexible Memory Configuration: Provides a DRAM remap option to logically reorder physical banks, useful for mapping out bad DRAM or configuring unsupported memory combinations without physical component changes. It generates control signals (RASBK#, CASBK, LBE) for DRAM banks.
• Expanded Memory Support: Offers full hardware support for the LIM EMS 4.0 standard, including 72 mapping registers and backfill capabilities down to 256KB, with flexible remapping of EMS page registers.
• Shadowing and Access Control: Supports memory shadowing across 16KB boundaries between 640KB and 1MB, allowing non-overlapping use of EMS, shadowed ROM, and direct system board access. It provides four distinct access options for read/write operations to different memory areas.
• Bus and Clock Control: Programs the operational mode of the AT bus, supplying the bus clock and signaling interface to the Bus Controller. It can run synchronously with the CPU's CLK2 or asynchronously via an external oscillator, with a programmable BUSCLK divider (1, 2, 3, or 4).
• Cache Integration: Includes special cache support to maintain performance with low-cost DRAMs at 33 MHz, designed for easy interfacing with the Intel 385DX cache controller.