Reviving a Computer System of 25 Years ago

Symposium at ETH 20.2.2014

Niklaus Wirth

www.inf.ethz.ch/personal/wirth/ProjectOberon

Programming Languages and Software Systems

•  Algol-W (at Stanford U. 1966) •  Pascal (1970) Structured programming •  Modula-2 (1979) Modular programming •  Windows, Menus, Icons (on computer Lilith) •  Oberon (1988) Object-oriented programming •  Oberon System (1990, on computer Ceres)

Personal Computers •  Alto at Xerox PARC (1975) •  Hi-res, memory-mapped display, Mouse •  Processor: TTL, 74S181 ALU (5.9 MHz) •  64K x 16 bit memory (1K bit chips!) •  2 MB cartridge disk (DEC) •  3 MHz Ethernet •  Inaugurates the age of computers •  Interactivity

Xerox Alto (1975)

Lilith (1980) •  Alto with newer technology •  Hi-res display, 640 x 800 pixels •  3 button mouse •  Processor: 4 AMD 2901 (7 MHz) •  64K 16 bit word memory •  10 MB cartridge disk (later 15MB disk) •  3 MHz Ethernet (1981) •  Central laser printer (Canon LBP-10) •  500 MB central file server (1982)

Lilith (1980)

Lilith (1982)

Ceres (1985, 1988)

•  Commercial microprocessor (NS32x32) •  Hi-res display (1024 x 800 pixels) •  2 MB memory (Ceres-1), 8 MB (Ceres-2) •  10 MHz clock (Ceres-1), 25 MHz (C-2) •  40 MB disk (Ceres-1), 80 MB disk (C-2) •  dual port RAM chips for display •  233 KHz network (low-cost)

Ceres-1 (1986)

Ceres-3 (1990)

Resurrecting Project Oberon

•  Project Oberon (Addison-Wesley, 1992) •  A rare book presenting all details of an

entire operating system and compiler •  Essential for engineering education •  Document of the State-of-the-Art of 1990 •  Bring it up to date and publish on Web! •  But …

•  NS-processor extinct – Large chapter on compiler is now irrelevant

•  Subject of storage mangement presented in obscure assembler code for NS processor

•  Same for raster operations for displaying characters and lines

•  Chapters on compiler, linking loader, garbage collection, and raster operations are either outdated or missing

•  Yet, most of the book can be retained

Consequences •  Design my own processor: RISC •  Implement this processor (with FPGA)

– Low-cost development board Spartan-3 – board contains 1 MB memory (SRAM) – disk replaced by CD-card (SPI interface)

•  Describe complete hardware (in Verilog) •  Rewrite chapters on compiler and linker •  Rewrite chapter on peripheral interfaces •  Describe all in Oberon, no assembler!

RISC (2013)

RISC on Spartan 3 (2013)

The processor RISC

Program counter Instr Reg

+ 1

Program Memory

adr

C0 +

decode

pcmux

off nxpc

IR, cond

Data

Register Bank

16 x 32

Data Memory

B C0

offset Shifter

adr

ALU

A

imm

+

regmux

PC IR

RISC instruction set 0 MOV a, n R.a := n 1 LSL a, b, n R.a := R.b ← n (shift left by n bits) 2 ASR a, b, n R.a := R.b → n (shift right by n bits) 3 ROR a, b, n R.a := R.b rot n (rotate right by n bits) 4 AND a, b, n R.a := R.b & n logical operations 5 ANN a, b, n R.a := R.b & ~n 6 IOR a, b, n R.a := R.b or n 7 XOR a, b, n R.a := R.b xor n 8 ADD a, b, n R.a := R.b + n integer arithmetic 9 SUB a, b, n R.a := R.b – n 10 MUL a, b, n R.a := R.a × n 11 DIV a, b, n R.a := R.b / n 12 FAD a, b, c R.a := R.b + R.c floating-point arithmetic 13 FSB a, b, c R.a := R.b – R.c 14 FML a, b, c R.a := R.a × R.c 15 FDV a, b, c R.a := R.b / R.c

What have I learnt?

•  Writing a program is difficult •  Writing a correct program is even more so •  Writing a publishable program is exacting

•  Programs are not written. They grow! •  Controlling growth needs much discipline •  Reducing size and complexity is the triumph

•  Programs must not be regarded as code for computers, but as literature for humans