Digital Research's original CP/M for the 8-bit Intel 8080 and Z-80 based systems spawned numerous spin-off versions, most notably CP/M-86 for the Intel 8086/8088 family of processors. Although CP/M had dominated the market, and was shipped with the vast majority of non-proprietary-architecture personal computers, the IBM PC in 1981 brought the beginning of what was eventually to be a massive change.
IBM originally approached Digital Research, seeking an x86 version of CP/M. However, there were disagreements over the contract, and IBM withdrew. Instead, a deal was struck with Microsoft, who purchased another operating system, 86-DOS, from Seattle Computer Products. This became Microsoft MS-DOS and IBM PC-DOS. 86-DOS' command structure and application programming interface imitated that of CP/M. Digital Research threatened legal action, claiming PC/MS-DOS to be too similar to CP/M. IBM settled by agreeing to sell their x86 version of CP/M, CP/M-86, alongside PC-DOS. However, PC-DOS sold for $60, while CP/M-86 had a $240 price tag. The proportion of PC buyers prepared to spend four times as much to buy CP/M-86 was very small, and the availability of compatible application software, at first decisively in Digital Research's favour, was only temporary.
Digital Research fought a long losing battle to promote CP/M-86, and eventually decided that they could not beat the Microsoft-IBM lead in application software availability, so they modified CP/M-86 to allow it to run the same applications as MS-DOS and PC-DOS. Initially, they sold DOS Plus, which ran applications for both platforms. It did not perform well, and Digital Research made another attempt, this time a fully DOS system. The new disk operating system was launched in 1988 as DR-DOS.
The first version was released in May, 1988. Version numbers were chosen to reflect features relative to MS-DOS; the first version promoted to the public was DR-DOS 3.41, which offered features comparable to the successful MS-DOS 3.3 and its derivatives.
At this time, MS-DOS was only available bundled with hardware, so DR-DOS achieved some immediate success as it was possible for consumers to buy it through normal retail channels. Also, DR-DOS was cheaper to license than MS-DOS. As a result, DRI was approached by a number of PC manufacturers who were interested in a third-party DOS, and this prompted several updates to the system.
First, the DR-DOS kernel and structures such as disk buffers can be located in the High Memory Area (HMA), the first 64KB of extended memory which are accessible in real mode due to an incomplete compatibility of the 80286 with earlier processors. This freed up the equivalent amount of critical "base" or conventional memory, the first 640KB of the PC's RAM – the area in which all MS-DOS applications run.
Additionally, on Intel 80386 machines, DR-DOS's EMS memory manager allowed the OS to load DOS device drivers into upper memory blocks, further freeing base memory. For more information on this, see the article on the Upper Memory Area (UMA).
DR-DOS 5 was the first DOS to integrate such functionality into the base OS (loading device drivers into upper memory blocks was possible using QEMM and MS-DOS). As such, on a 386 system, it could offer vastly more free conventional memory than any other DOS. Once drivers for a mouse, multimedia hardware and a network stack were loaded, an MS-DOS machine typically might only have 300 to 400KB of free conventional memory – too little to run most late-1980s software. DR-DOS 5, with a small amount of manual tweaking, could load all this and still keep all of its conventional memory free – allowing for some necessary DOS data structures, as much as 620KB out of the 640KB.
Because DR-DOS leaves so much conventional memory available, some programs fail to load as they start "impossibly" low in memory – inside the first 64KB. DR-DOS 5's new LOADFIX command works around this by leaving a small empty space at the start of the memory map.
Faced with substantial competition in the DOS arena, Microsoft responded strongly. They announced the development of MS-DOS 5.0 in May 1990, to be released in 1991 and include similar advanced features to those of DR-DOS. It included matches of the DR's enhancements in memory management.
DR responded with DR-DOS 6.0 in 1991. This bundled in SuperStor on-the-fly disk compression, to maximise available hard disk space. DR-DOS 6.0 also includes an API for multitasking on CPUs capable of memory protection, namely the Intel 80286 and newer. The API was available only to DR-DOS aware applications, but well-behaved ordinary DOS applications can also be pre-emptively multitasked by the bundled task-switcher, TaskMax. On 286-based systems, which only allow a single process to execute simultaneously, DOS applications are suspended to the background to allow others to run.
Microsoft responded with MS-DOS 6.0, which again matched some features of DR-DOS 6.0.
Though DR-DOS was apparently 100% binary compatible with applications written for MS-DOS, Microsoft nevertheless expended considerable effort in attempts to break compatibility. In one example, they inserted code into a beta version Windows 3.1 to return a non-fatal error message if it detected a non-Microsoft DOS. This check came to be known as the AARD code. With the detection code disabled, Windows ran perfectly under DR-DOS and its successor Novell DOS. The code was present, but disabled in the released version of Windows 3.1
At about this time Digital Research also embarked on a spin-off Product called PalmDOS (and later released as Netware PalmDOS), which as its name implies was a DR-DOS derivative aimed at the emerging Palmtop/PDA market.
As well as a ROM-executing kernel it had palmtop-type support for features such as PCMCIA PC Cards, Power Management, etc.
The PalmDOS project was lead by Ian Cullimore.
Although DRI was based in Monterey, California, most of the operating system work (especially DR-DOS, Multiuser DOS and PalmDOS) was done in Hungerford, UK.
It was a simple matter for Digital Research to patch DR-DOS to circumvent the 'authenticity check' in Windows 3.1 beta, and the patched version was on the streets within six weeks of the release of Windows 3.1. With improved marketing and packaging, very advanced memory management, disk compression and the Super PC-Kwik caching software, DR-DOS 6.0 was an outstanding value and easily the most successful version.
Around this time, networking giant Novell bought Digital Research with a view to using DR's product line as a lever in their comprehensive strategy to break the Microsoft monopoly. (This was part of a massive and ultimately disastrous spending spree for Novell: they bought WordPerfect Corporation at about the same time, some of Borland's products, and invested heavily in Unix as well.) The planned DR-DOS 7.0, intended to trump Microsoft's troubled MS-DOS 6.0, was repeatedly delayed. When it eventually arrived – renamed to Novell DOS 7.0 – it was a disappointment. It was bigger and introduced many new bugs and the main functional addition was Novell's second attempt at a peer-to-peer networking system, Personal Netware. This worked and was better than its predecessor Netware Lite but it was incompatible with Microsoft's networking system, now growing popular with support in Windows for Workgroups, OS/2 and Windows NT. A considerable amount of manual configuration was needed to get both to co-exist on the same PC, and Personal Netware never achieved much success.
Caldera released the operating system as open source, under the name "Caldera OpenDOS". OpenDOS was released as version 7.01 and 7.02, and the source was then closed. (Version 7.02 was called "Caldera OpenDOS 7.02" while in beta testing; by the time it was released in December of 1997, it was branded "Caldera DR-OpenDOS 7.02". The next release came in March of 1998; it was branded "Caldera DR DOS 7.02") Another version was released, 7.03, before Caldera transferred the DR DOS line to a branch company, Caldera Thin Clients, which would become Lineo. Lineo would later release revisions of 7.03, still branded as "Caldera DR DOS
The last Lineo version was DR DOS 7.04/7.05, still branded as "Caldera DR DOS". This was an embedded system consisting only of the kernel and command shell. It was built for Seagate Technology's Seatools, with a buggy implementation of FAT32 and large hard disk support.
The OpenDOS 7.01 source code is still actively being developed by The DR-DOS/OpenDOS Enhancement Project, founded in July 2002 in an attempt to bring the functionality of DR-DOS up to parity with modern PC operating systems. The project's efforts have resulted so far in adding native support for large disks (LBA) and the FAT32 filesystem. There were also several other enhancements, including improved memory management and support for the new FAT+ filesystem extension which allows files of almost 256 GB in size on normal FAT partitions.
In 2002, Lineo was bought out, and some of Lineo's former managers purchased the name and formed a new company, DeviceLogics. They have continued to sell DR-DOS for use in embedded systems. DR-DOS 8.0 was released on 30 March 2004 featuring FAT32 and large disk support, the ability to boot from ROM or Flash, multitasking and a DPMI memory manager. This version was based on the kernel from version 7.03.The company then split into Devicelogics Inc. and DRDOS Inc, which released DR-DOS 8.1 (with better FAT32 support) in autumn 2005. This version was not based upon version 8.0, but was a complete rewrite. Both 8.0 and 8.1 have now been pulled (because of the discoveries outlined below), and replaced with Caldera DR DOS 7.03.
Aside from selling copies of the operating system, the DR DOS Inc. website lists a buyout option for DR DOS; the asking price is $25,000.
In October 2005, it was discovered that DR-DOS 8.1 included several utilities from FreeDOS and other sources and that the kernel was an outdated version of the Enhanced DR-DOS kernel. DR-DOS Inc. failed to comply with the GNU General Public License (GPL) by not crediting the FreeDOS utilities to their authors and including the source code. After complaints from FreeDOS developers (including the suggestion to provide the source code, and hence comply with the GPL), DR DOS Inc. instead pulled all 8.x versions (including the unaffected DR-DOS 8.0) from their website.
DR DOS 6.0 is an operating system that really works. (Digital Research Inc.) (Software Review) (IBM) (Evaluation)
Feb 01, 1992; For years, industry experts have assured us that the next version of DOS will be what DOS should have been all along. DOS 5.0 was...
Memory management: DR DOS 6.0 vs. DOS 5.0. (operating systems)(includes related article examining the CONFIG and AUTOEXEC files as they relate to DR DOS and MS-DOS) (Software Review) (Tech Section) (Evaluation)
Feb 01, 1992; Slugfest: DOS 5.0 vs. DR DOS 6.0 Installations The CONFIG and AUTOEXEC files in most systems work through a delicate combination...