CPM3.SYS
| Industry | Software, Operating systems |
|---|---|
| Founded | 1974 |
| Founder | Gary Kildall |
| Headquarters | United States |
| Products | CP/M, CP/M-86, MP/M-86, Concurrent CP/M-86, Concurrent DOS, Multiuser DOS, REAL/32, FlexOS, DOS Plus, DR DOS |
CP/M-86 represents a now-obsolete variant of the CP/M operating system, developed by Digital Research (DR) specifically for the Intel 8086 and Intel 8088 CPU architectures. It maintained compatibility with CP/M-80 system commands, utilizing relocatable executables in the .CMD file format. Digital Research also produced MP/M-86, a multitasking, multi-user OS compatible with CP/M-86, which later evolved into Concurrent CP/M-86. Incorporating a PC DOS emulator led to its rebranding as Concurrent DOS, which eventually became Multiuser DOS, with its most recent iteration known as REAL/32. Operating systems such as FlexOS, DOS Plus, and DR DOS trace their origins back to Concurrent DOS.
History
Although Digital Research initially planned to release CP/M-86 in November 1979, the launch encountered multiple postponements. When IBM searched for an operating system for the IBM PC, CP/M-86 was favored due to its extensive software ecosystem. However, negotiations broke down because IBM insisted on a non-disclosure agreement and preferred a one-time payment, conflicting with Digital Research’s royalty-based pricing model. Following talks with Microsoft, IBM opted for 86-DOS (also known as QDOS), an OS resembling CP/M that Microsoft had acquired and modified into MS-DOS, subsequently licensing it to IBM as PC DOS. Digital Research founder Gary Kildall threatened legal action over intellectual property issues, prompting IBM to offer CP/M-86 as an alternative OS for the PC. The majority of CP/M-86 BIOS drivers were created by Andy Johnson-Laird.
The IBM PC debuted in August 1981, 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 introduction in early 1982; porting software from CP/M-80 proved equally challenging on both platforms. Additionally, in November 1981, Digital Research launched a CP/M-86 version tailored for the proprietary IBM Displaywriter.
Certain dual-processor systems combining 8-bit and 16-bit CPUs supported specialized CP/M-86 versions capable of running both CP/M-86 and CP/M-80 applications natively. For instance, the DEC Rainbow utilized CP/M-86/80, while the CompuPro System 816 operated CP/M 8-16. The Zenith Z-100 was compatible with software designed for both its 8085 and 8088 processors.
As IBM PC clones gained popularity, Microsoft broadly licensed MS-DOS. Technical assessments indicated that CP/M-86 and MS-DOS offered comparable capabilities—CP/M-86 featured more advanced memory management, whereas MS-DOS excelled in speed. BYTE magazine observed that Microsoft’s emphasis on multitasking through Xenix left room in the market for Concurrent CP/M-86.
Nevertheless, at $240 per license compared to PC DOS’s $40 price point, CP/M-86 experienced poor sales; surveys revealed that 96.3% of IBM PCs shipped with DOS, while only 3.4% carried either CP/M-86 or Concurrent CP/M-86. Lifeboat Associates, a prominent distributor of CP/M software, shifted allegiance to DOS by mid-1982. BYTE cautioned that support from IBM, Microsoft, and Lifeboat for DOS posed a significant threat to CP/M-86’s market position; industry analysts attributed this decline partly to Digital Research’s marketing shortcomings.
By early 1983, Digital Research offered version 1.1 of CP/M-86 directly to consumers at $60 per copy, promoting it as providing access to the largest available software library and including Graphics System Extension (GSX). The company also expanded retail distribution channels. In May 1983, Digital Research announced DOS-compatible versions of its programming languages and utilities, acknowledging DOS’s market dominance but denying it influenced their strategy. By early 1984, Digital Research bundled free copies of Concurrent CP/M-86 with purchases of two CP/M-86 applications; these applications were distributed on self-booting disks that did not require loading the operating system first.
In January 1984, Digital Research introduced Kanji CP/M-86 aimed at nine Japanese corporations such as Mitsubishi Electric and Sanyo Electric; subsequently, Fujitsu announced FM-16 computers running Kanji CP/M-86.
While sharing similar functionality, CP/M-86 and MS-DOS were incompatible due to different system call interfaces and file formats, necessitating distinct software versions for each platform. Their command-line environments offered comparable features but differed syntactically—for example, file copying employed PIP under CP/M versus COPY in DOS.
Initially, both MS-DOS and CP/M-86 operated on non-PC-compatible hardware like Apricot and Sirius systems by adapting OS calls to specific hardware configurations. However, performance-sensitive programs accessed IBM PC hardware directly to maximize speed advantages, driving widespread adoption of PC-compatible architectures. This standardization imposed a 640 KB memory ceiling on subsequent machines running these operating systems; earlier models did not encounter this limitation and could utilize nearly one megabyte of RAM.
Reception
PC Magazine observed that CP/M-86 appeared, in multiple respects, to be more suitably designed for the PC than DOS. Nevertheless, its price—being six times greater—deterred many users who did not engage in assembly language programming. The review underscored the areas where CP/M-86 excelled compared to DOS, and vice versa, stressing that the availability of applications would ultimately determine user preference. A significant limitation was the absence of a run-time version for CP/M-86 applications.
Versions
CP/M-86 releases are identified by two version numbers: one representing the entire operating system (displayed at startup) and another for the BDOS kernel component. Some recognized versions include:
| Operating System | BDOS Version | Release Date | Remarks |
|---|---|---|---|
| CP/M-86 1.0 for AST | Approximately 2.2 | Circa 1981 | |
| CP/M-86 1.0 for Altos ACS 16000/ACS 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 | Supported 196 KB disk capacity; compatible with IBM PC hardware |
| IBM CP/M-86 for IBM Personal Computer Version 1.0 | 2.2 | April 1982 | Initial launch; supported disks up to 141 KB |
| IBM CP/M-86 Version 1.1 | 2.2 | March 1983 | Introduced hard drive compatibility |
| CP/M-86 Plus Version 3.1 | 3.1 | October 1983 | Designed for Apricot PC, featuring a multitasking kernel capable of running four tasks simultaneously |
| Personal CP/M-86 Version 1.0 | 3.1 | November 1983 | Released for Siemens Siemens PG685 |
| Personal CP/M-86 Version 3.1 | 3.3 | January 1985 | Targeted Apricot Computers Apricot F-Series, added FAT disk support compatible with DOS |
| Personal CP/M-86 Version 2.0 | 4.1 | From 1986 onward | For Siemens PC16-20, incorporating BDOS from DOS Plus 1.2 |
| Personal CP/M-86 Version 2.11 | 4.1 | From 1986 onward | Designed for Siemens PG685 |
All iterations of Personal CP/M-86 are based on the CP/M-86 Plus source code, indicating a shared lineage.
In addition, various Eastern Bloc adaptations of CP/M-86 circulated under names such as SCP1700 (Single User Control Program), CP/K, and K8918-OS, developed by East German manufacturers like VEB Robotron Dresden and Energiekombinat Berlin.
Legacy
Starting in 1997, Caldera granted permission to redistribute and modify all original Digital Research materials, including the source code of the CP/M series, through Tim Olmstead's "The Unofficial CP/M Web site." Following Olmstead's passing in September 2001, Lineo, then custodian of these Digital Research assets, renewed and broadened the free distribution license in October of the same year.
Further reading
- The Byte Guide to CP/M-86 authored by Mark Dahmke, published by McGraw-Hill in 1984, ISBN 978-0-07-015072-0
External links
- The Unofficial CP/M Website – authorized distributor of original Digital Research software
- The comp.os.cpm FAQ
- Intel iPDS-100 Using CP/M Video