The Olivetti M20 is a Zilog Z8000 based computer from Olivetti introduced in 1982. Although it offered good performance, it suffered from a lack of software due to its use of the Z8000 processor and custom operating system, PCOS. The company introduced an IBM PC compatible in January 1984 and the M20 line was phased out.

Olivetti M20
Model BC distributed in Italy
TypePersonal computer
Release date1982; 38 years ago (1982)
Operating systemPCOS
CPUZilog Z8001 @ 4 MHz
Memory128 KB (expandable to 512 KB)
SuccessorOlivetti M24


System design began in 1979 in Cupertino (California) at Olivetti's Advanced Technology Center.[1]:189 When announced on March 31, 1982,[2]:1 it was probably the first 16-bit personal computer in Europe with an expected price range of US$3,000-6,000.[2]:10

InfoWorld magazine saw the M20 as an "answer to Tandy's Model 16, the IBM Personal Computer and the Apple III";[3] Olivetti itself compared its computer to the IBM PC, Sirius Victor, Commodore 8000 and Apple II in television advertising.[4]

Although the computer was initially well received,[5] its use of a non-standard OS (Olivetti's proprietary PCOS) and CPU (Zilog Z8001) proved to be its most serious limitations.[1]:192[6]:13 The first major software package was a word processor by SofSys called Executive Secretary,[7] followed later by another word processor, OliWord, and business software, Olibiz. There was also Microsoft BASIC 5.2 with full support for the hardware's features.[6]:14

To alleviate a lack of applications, Olivetti sold a CP/M emulator for US$300 and distributed certain CP/M software packages (dBase II and SuperCalc) for their computer.[7] Olivetti later introduced the "Alternate Processor Board" (APB 1086), based on an 8 MHz Intel 8086 CPU for compatibility with MS-DOS and CP/M-86 software.[1]:192

In January 1984, Olivetti introduced a new IBM PC-compatible computer running MS-DOS as a "complement" to the Olivetti M20.[8]

Olivetti sold around 50,000 M20 computers in the first year of production.[1]:189


Olivetti M20 motherboard
Zilog 8001 on the motherboard of an Olivetti M20 computer

M20 uses Zilog Z8001 4 MHz CPU and 128 KB RAM,[6]:14 which can be expanded up to 512 KB by three 128 KB memory boards.[1]:190 Keyboard, motherboard and disk drives are contained in all-in-one unit with separate monitor.[6]:13 The computer has also parallel (IEEE-488) and serial port (RS-232-C). Standard configuration[nb 1] includes two 5¼-inch 320 KB floppy disk drives (286 KB formatted capacity). Optional were 160 KB or 640 KB (compatible with 320 KB disks) drives or 5¼-inch hard disk in place of one of the floppy disk drives (9.2 MB formatted capacity).[1]:190

Motherboard has two expansion slots intended for the hard disk controller board, additional parallel interface, twin serial interface or Corvus Omninet LAN card.[1]:190 This slot is also used by the APB 1086 CPU card.[11]:2-86

M20 provides 512 × 256 display resolution on 12-inch[9] monochrome or color monitor. With memory expanded by two 32 KB memory boards, the computer can display 8 colors. When using only one additional memory board, only 4 colors form 8 color palette are available. All graphics is pixel-generated (there is no specific text mode), text characters use resolution 64 characters per 16 rows (or 80 characters per 25 rows).[1]:190

Keyboard lacks delete, tab and backspace keys - their function can be mapped on S1 or S2 special keys by the "Change Key" system utility. Instead of standard function keys, user defined special functions are invoked by pressing orange-colored "Command" or light-blue-colored "Control" key along with another key (creates 24 user-definable function keys). Numeric keypad serves also as cursor controls.[1]:189


PCOS (Professional Computer Operating System[6]:13) is a single-user, single-tasking operating system.[1]:191 PCOS requires significant part of the main memory.[6]:13 Operating system with BASIC interpreter takes 64 KB RAM,[11]:2-15 another 16 KB are reserved for screen output and user is left with only around 40 KB RAM on unexpanded machine. Version 2.0 supports dynamic memory allocation alleviating segmented memory limitations of the Z8000 CPU.[1]:191 PCOS can protect by password volumes (disks), individual files and BASIC programs (against listing/editing/copying).[1]:192 Standard OS configuration includes BASIC interpreter, other programming languages (Assembler and PASCAL) are optional.[12]


  1. ^ Announced price for basic configuration with only one 320 KB floppy disk drive was US$2,965.[9] Price of M20 including monitor, two 320 KB floppy disk drives, PCOS and BASIC was NZ$6,850 in June 1983. Dual 640 KB floppy disk drives were available for additional NZ$2,200, 32 KB memory expansion for NZ$430 and PR 1450 printer for NZ$2,450. Total system price with hard drive could reach NZ$17,000. Software packgages Olibiz and OliWord cost both around NZ$400.[6]:14 Exchange rate in June 1983 was US$0.6569 for NZ$1.[10]


  1. ^ a b c d e f g h i j k l Mello-Grand, Sergio (June 1983). "The Docutel/Olivetti M20 A Sleek Import". Byte. Vol. 8 no. 6. Byte Publications. pp. 188–192. ISSN 0360-5280.
  2. ^ a b Freiberger, Paul (April 19, 1982). "Olivetti microcomputer debuts, M20 will be one of the first 16-bit systems in Europe". InfoWorld. Vol. 4 no. 13. IDG. pp. 1, 10. ISSN 0199-6649.
  3. ^ Freiberger, Paul (May 24, 1982). "Olivetti´s new M20 confronts top micros". InfoWorld. Vol. 4 no. 20. IDG. p. 3. ISSN 0199-6649.
  4. ^ Kewney, Guy (May 23, 1983). "M20 embarrasses Olivetti execs at Hannover Fair". InfoWorld. Vol. 5 no. 21. IDG. p. 30. ISSN 0199-6649.
  5. ^ Kewney, Guy (May 17, 1982). "Micro firms vie dor European market at Hannover". InfoWorld. Vol. 4 no. 19. IDG. p. 5. ISSN 0199-6649.
  6. ^ a b c d e f g Marett, Warren (June 1983). "Italian micro enters New Zealand business market". Bits and Bytes. No. 9. Neill Birss, Dion Crooks and Paul Crooks. pp. 13–14, 33. ISSN 0111-9826.
  7. ^ a b Freiberger, Paul (October 4, 1982). "Olivetti releases software, announces plans for M20". InfoWorld. Vol. 4 no. 39. IDG. p. 15. ISSN 0199-6649.
  8. ^ "Late news, Olivetti unveils PC-compatible". InfoWorld. Vol. 6 no. 5. IDG. January 30, 1984. p. 9. ISSN 0199-6649.
  9. ^ a b Free, John (August 1982). "Bits & Bytes". Popular Science. Vol. 221 no. 2. Times Mirror Magazines. p. 42. ISSN 0161-7370.
  10. ^ "Monthly exchange rates and TWI - B1". Reserve Bank of New Zealand. September 4, 2017. Archived from the original (XLSX) on January 28, 2018. Retrieved May 31, 2018.
  11. ^ a b The Olivetti L1 M20 Hardware Architecture and Function Manual. Ivrea, Italy: Olivetti. July 1983.
  12. ^ M20 Personal Computer PCOS (Professional Computer Operating System) User Guide. Ivrea, Italy: Olivetti. June 1983. p. 1-1.

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