MK11 MOS memory technical manual

This technical manual describes the Digital Equipment Corporation (DEC) MK11 MOS memory system, designed for use with PDP-11/70 computers. The MK11 provides up to 4 megabytes of main memory, structured in 39-bit double-word blocks (32 data bits and 7 error-correction-code check bits) stored in dynamic MOS random-access arrays. Its key feature is an Error Correction Code (ECC) capable of correcting all single-bit errors and detecting all double-bit errors.

The system is physically organized into a BA11 box, a box controller, and battery backup units. The BA11 box houses the MS11-K MOS memory array modules (containing 4K MOS RAM chips), an Address Buffer Module (M8158), a Data Buffer Module (M8159) which includes the Control and Status Register (CSR), and Control A/B Modules (M8160/M8161) responsible for timing, control, and ECC functions. Each BA11 box can contain 64K to 512K words, with expanded systems supporting up to 2 million words across multiple memory cabinets. Battery backup units provide power for memory refresh during AC line transients for at least 5 minutes.

The manual details the main memory bus interface to the PDP-11/70 cache, outlining read, write (including internal read-modify-write for partial byte operations), and exchange cycles, along with their protocols and timing. It also covers refresh and ECC initialization cycles. The box controller allows operators to select starting addresses, external interleaving, and ECC enable/disable modes, and provides status indicators.

Comprehensive instructions are provided for installing and configuring the memory system, including adding array modules, memory boxes, and secondary memory cabinets, with specific attention to cable routing and proper component installation. Power supply and distribution are detailed, with procedures for voltage measurement, adjustment, and subassembly removal.

For maintenance, the document describes a diagnostic program that generates configuration maps, provides detailed error reports, and offers a field service mode for in-depth testing. It includes troubleshooting flowcharts to isolate faults in memory modules, data buffers, control modules, or cabling, and procedures to verify ECC initialization and boot characteristics.