ND-110 CPU

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Introduction

The ND-110 is an improvement over the ND-100 in a number of areas.

• Size. The CPU, the Memory Management System, cache memory and operator panel processor is combined on one single board.
• New technology. The CPU is constructed by a gate-array. The CPU concists of three VLSI gate arrays, RMIC, RMAC and BUFALU. The ND-110 CPU is also making extensive usage of programmable logic.
• New cache memory strategy. The first micro instruction word of a macroinstruction is stored in cache memory.
• Address arithmetic. Address arithmetic is performed in the RMAC gate array, not by the micro code as in ND-100.
• The interrupt system. Unlike the ND-100 CPU, the ND-110 (and ND-100/CX) CPU handles synchronous interrupts as traps, in a similar way as ND-500 does.
• The Control Store. The control store is based on fast read/write RAM instead of PROM. At power up the memory is initialised from two 8 kbyte EPROMs. The control store can be read or modified by program.
• Control logic and timing. Much of the control and timing logic have been moved into PAL chips. The main crystal oscillator is now a 39.3216 MHz oscillator. It is used for the nano-sequencer, the CPU-clock, the bus arbiter, the real time clock and the console UART. The nano-sequencer is a four bit state machine used for timing and control.
• Power consumption. The power consumption was reduced from 90 watts to 60.

The VLSI chips

• The Micro Instruction Controller, the MIC - also known as RMIC, for "Rask MIC" ("Speedy MIC"). It replaced three 74S482 sequencers and about 30 other ICs.
• The Arithmetical and Logical Unit gate array (ALU, also known as the "BUFALU"). Replaced four Am2901 bit-slice processors, and some additional registers like the data bus register the general purpose register, and the internal register block.
• The Micro Address Controller (The MAC, also called RMAC, for "Rask MAC" ("Speedy MAC"). It implemented hardware address arithmetic, which in the ND-100 had been done in microcode.

Cache memory details

In addition to the macro-instruction cache memory also found in the ND-100, the ND-110 had a unique implementation of cache memory on the micro-instruction level. The step known as mapping in the ND-100 was then avoided because the first micro-instruction word of a macro-instruction was written into the control store cache.

Versions

The ND-110 CPU comes in two versions. A standard version and a fast version. Depending on application the ND-110/CX is 1.5 to 3.5 times faster than ND-110. Both versions comes with memory management, a new type of cache memory and the commercial extended instruction set as standard.

ND-110

This is the standard ND-110 version. It has the same performance as the ND-100/CX. It has a 1k word instruction cache and executes with 0.32 Whetstone MIPS.

ND-110/CX

This is the fast version of the ND-110 CPU. It is 1.5-3.5 faster than the standard version. It has a 4k word instruction and data cache and executes with 0.55 Whetstone MIPS.

Print versions

• 3090 An early version of the CPU with two different print release versions (C, K)
• 3095 A later version of the CPU, only known print release version is B.

New instructions

• TRA CS - Reads 16 control storage bits into the A-register. The X-register contains the store address.
• TRR CS - Writes the A-register into 16 control store bits. The X-register contains the control store address.
• TRR CILP - Cache inhibit individual page.
• VERSN - Reads version numbers of print and micro program.
• SETPT - Set page tables.
• CLEPT - Clear page tables.
• CLNREENT - Clear non re-entrant pages.
• CHREENTPAGES - Change page tables.
• CLEPU - Clear page tables and collect PGU information.
• WGLOB - Initialize global pointers.
• RGLOB - Examine global pointers.
• INSPL - Insert page in page list.
• REMPL - Remove page from page list.
• CNREK - Clear non re-entrant pages.
• CLPT - Clear segment from page tables.
• ENPT - Enter segment in page tables.
• REPT - Enter re-entrant segment in page tables.
• LBIT - Load single bit accumulator (K) with logical memory bit.
• SBITP - Store single bit accumulator (K) in a physical memory bit.
• LBYTP - Load the A register with a single byte from physical memory.
• SBYTP - Store single byte in physical memory.
• TSETP - Test and set a physical memory word.
• RDUSP - Read a physical memory word without using cache.
• LASB - Load the A register with the contents of the segment-table bank (STBNK).
• SASB - Store the A register contents in the STBNK.
• LACB - Load the A register with the contents of the core map-table bank (CMBNK).
• SACB - Store the A register contents in the CMBNK.
• LXSB - Load the X register with the contents of the STBNK.
• LXCB - Load the X register with the contents of the CMBNK.
• SZSB - Store zero in the STBNK.
• SZCB - Store zero in the CMBNK.

Microcode format

The ND-110/CX microcode format is described in Norsk Data Document ND–06.026 ND-110 Functional Description (ND-06.026.01 rev A page 235).

There is a surviving list of the microcode version K in Telemuseums storage in Fetsund. It's not easy to read and almost 200 pages of code. Interestingly enough, there are some mention of SINTRAN IV in the code.

Reference and Sources

• Norsk Data Document ND–06.026 ND-110 Functional Description (ND-06.026.01 rev A)