CP/M 8-16
| Industry | Software, Operating systems |
|---|---|
| Founded | 1974 |
| Founder | Gary Kildall |
| Products | CP/M, CP/M-86, MP/M-86, Concurrent CP/M-86, Concurrent DOS, Multiuser DOS, REAL/32, FlexOS, DOS Plus, DR DOS |
| Website | www |
CP/M-86 represents a now-obsolete iteration of the CP/M operating system, crafted by Digital Research (DR) for use with the Intel 8086 and Intel 8088 CPUs. It retained compatibility with CP/M-80 system commands and utilized the relocatable .CMD file format for executable programs.[nb 1] Digital Research also developed MP/M-86, a multi-user multitasking OS compatible with CP/M-86, which later evolved into Concurrent CP/M-86. By incorporating an emulator to support PC DOS applications, this platform was renamed Concurrent DOS, and subsequently rebranded as Multiuser DOS, with its latest iteration known as REAL/32. The families of FlexOS, DOS Plus, and DR DOS trace their origins back to Concurrent DOS derivatives.
History
Initially slated for release in November 1979, Digital Research’s CP/M-86 experienced multiple postponements. When IBM sought an operating system for its forthcoming IBM PC, CP/M-86 was favored due to its extensive software ecosystem. However, negotiations collapsed because IBM insisted on a non-disclosure agreement and preferred a single payment rather than Digital Research’s royalty-based pricing. Consequently, IBM turned to Microsoft, licensing 86-DOS (QDOS), which Microsoft adapted and marketed as PC DOS. Upon discovering this arrangement, Digital Research founder Gary Kildall threatened legal action, leading IBM to offer CP/M-86 as an alternative OS option for the PC. The majority of CP/M-86 BIOS drivers for the IBM PC were developed by Andy Johnson-Laird.
The IBM PC debuted in August 1981 and began shipping in October, providing users with three operating system choices: PC DOS, CP/M-86, and UCSD p-System. Digital Research released CP/M-86 for the IBM PC approximately six months after PC DOS’s launch in spring 1982; porting applications from CP/M-80 presented similar challenges across both operating systems. Additionally, a version tailored for the proprietary IBM Displaywriter was issued in November 1981.
Certain dual-processor systems combining 8-bit and 16-bit architectures supported specialized versions of CP/M-86 capable of running both CP/M-86 and CP/M-80 programs. For instance, the DEC Rainbow operated with CP/M-86/80, while CompuPro System 816 used CP/M 8-16. The Zenith Z-100 was compatible with software designed for both 8085 and 8088 processors.
As PC clones gained market traction, Microsoft widely licensed MS-DOS. Analysts observed that while CP/M-86 offered more advanced memory management features, DOS delivered superior speed performance. BYTE magazine noted that Microsoft’s investment in multitasking through Xenix created space for Concurrent CP/M-86 in the marketplace.
Despite these technical merits, CP/M-86’s retail price stood at $240 per license compared to PC DOS’s $40, resulting in significantly lower sales; market surveys indicated that 96.3% of IBM PCs were shipped with DOS installed versus only 3.4% featuring CP/M-86 or Concurrent CP/M-86. By mid-1982, prominent software publishers such as Lifeboat Associates shifted their support toward DOS. BYTE warned that such trends jeopardized CP/M-86’s position in the market, with industry commentators attributing this to Digital Research’s inadequate marketing strategies.
By early 1983, Digital Research began selling version 1.1 of CP/M-86 directly to end users at a reduced price of $60 per copy, promoting it as providing access to the largest available application library and bundling the Graphics System Extension (GSX). The company expanded its product distribution through retail software channels and announced plans in May 1983 to release DOS-compatible versions of its programming languages and utilities—acknowledging PC DOS’s dominance but denying it influenced their decision. Early promotional efforts in 1984 included offering free Concurrent CP/M-86 copies bundled with applications and distributing self-booting disks that circumvented the need to load the OS separately.
In January 1984, Digital Research launched Kanji CP/M-86 aimed at Japanese enterprises such as Mitsubishi Electric and Sanyo Electric; subsequently, Fujitsu announced FM-16 models running Kanji CP/M-86.
Although both CP/M-86 and DOS provided comparable functionalities, they remained incompatible due to differences in system calls and executable file formats—requiring distinct software versions tailored to each platform. Their command-line interfaces offered similar capabilities but differed syntactically; for example, copying files involved PIP TARGET=SOURCE on CP/M-86 versus COPY SOURCE TARGET under DOS.
Initially, MS-DOS and CP/M-86 operated on hardware platforms not fully compatible with the IBM PC—such as Apricot and Sirius systems—by adapting OS calls to specific hardware configurations. Nevertheless, performance-sensitive applications—especially games—accessed hardware directly and thus favored PC-compatible architectures. This trend led to widespread adoption of PC-compatible hardware designs but imposed a conventional memory limitation of 640 KB not present on early MS-DOS or CP/M-86 systems capable of utilizing nearly one megabyte of RAM.
Reception
PC Magazine observed that CP/M-86 appeared, in multiple respects, to be better suited for the PC environment compared to DOS; nevertheless, its significantly higher cost—approximately six times greater—deterred users who did not engage in assembly language programming. The review underscored the areas where CP/M-86 excelled relative to DOS and vice versa, stressing that the availability of application software would ultimately determine user preference. A significant drawback identified was CP/M-86's absence of a run-time version for executing applications.
Versions
CP/M-86 releases are characterized by two version numbers: one representing the entire operating system (shown during startup) and another denoting the BDOS kernel iteration. Important versions include:
| Operating System | BDOS Version | Release Date | Remarks |
|---|---|---|---|
| CP/M-86 1.0 tailored for AST Research | Approximately 2.2 | Circa 1981 | |
| CP/M-86 1.0 designed for Altos Computer Systems ACS 16000/8600 | Approximately 2.2 | November 1981 | |
| CP/M-86 Version 1.1 for IBM Displaywriter | 2.2 | November 1981 | |
| CP/M-86 1.0 for Sirius 1/Victor 9000 | 2.2a | Between 1981 and 1982 | |
| CompuView CP/M-86 | Around 2.x | 1982 | Supports 196 KB disk capacity; compatible with IBM PC hardware |
| IBM CP/M-86 Version 1.0 for IBM Personal Computer | 2.2 | April 1982 | Initial launch; disk capacity of 141 KB |
| IBM CP/M-86 Version 1.1 for IBM PC | 2.2 | March 1983 | Introduced hard drive compatibility |
| CP/M-86 Plus Version 3.1 | 3.1 | October 1983 | Developed for Apricot PC; multitasking kernel capable of managing up to four simultaneous tasks |
| Personal CP/M-86 Version 1.0 | 3.1 | November 1983 | Released specifically for Siemens PG685 |
| Personal CP/M-86 Version 3.1 | 3.3 | January 1985 | Designed for Apricot Computers F-Series; incorporated FAT file system support |
| Personal CP/M-86 Version 2.0 | 4.1 | From 1986 onward | Intended for Siemens PC16-20; utilizes the same BDOS as DOS Plus 1.2 |
| Personal CP/M-86 Version 2.11 | 4.1 | From 1986 onward | Targeted at Siemens PG685 |
All variants under the Personal CP/M-86 designation are derived from the CP/M-86 Plus codebase.
In addition, several Eastern Bloc adaptations emerged under various titles such as SCP1700, CP/K, and K8918-OS, developed by East German companies like VEB Robotron Dresden and Energiekombinat Berlin, representing localized versions of the CP/M-86 system.
Legacy
Starting in 1997, Caldera authorized the redistribution and modification of all original Digital Research materials, including source code for the entire CP/M series, through Tim Olmstead's "The Unofficial CP/M Web site." Following Olmstead’s passing in September 2001, Lineo, then holding ownership of Digital Research assets, renewed and broadened this free distribution license in October of that year.
See also
Further reading
- The Byte Guide to CP/M-86 by Mark Dahmke (1984), McGraw-Hill, ISBN 978-0-07-015072-0
External links
- The Unofficial CP/M Website – authorized source for original Digital Research software
- The comp.os.cpm FAQ
- Intel iPDS-100 Using CP/M Video
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