SDL Sopwith

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History of Sopwith

Illustration: Sopwith start screen

At the time of writing, Sopwith is approaching its 40th birthday. Sopwith is a very old game, and has an interesting history that deserves to be documented.

First released in 1984, Sopwith was one of the first games for the IBM PC. Released less than three years after the release of the IBM PC in August 1981, Sopwith sits within the “first wave” of games developed for the system. The PC remains an important platform for games to this day.

Sopwith is one of the earliest networked games, and indeed was developed as a demo program for the proprietary Imaginet system, an early form of LAN Certainly there are other earlier and contemporary examples, including Maze War and SGI Dogfight; Sopwith was not the first. However, at the time of its release there were still relatively few other examples. An unfortunate detail is that the game only worked with the proprietary BMB hardware and drivers, meaning that very few people were able to use this feature.

Sopwith is one of the oldest video games still in active development today. In 2018, PC Gamer published a list of old games still being maintained and developed. Sopwith is not on the list, but the only game on the list arguably older is Hack (1984), released several months earlier and still under development in the form of NetHack. SDL Sopwith is directly derived from the source code to the original DOS versions, and still includes changelog comments that date all the way back to 1984.

About BMB Compuscience

Illustration: BMB Compuscience logo

BMB Compuscience was a Canadian company founded in 1979 and based in Milton, Ontario by Bill MacLean, Marcel Brunschweiler and Barbara Brunschweiler. The initials of their first names were the origin of the name BMB. The business originally acted as a reseller for Commodore computers, targeting scientists and researchers. BMB then pivoted to focus on the IBM PC after it was released in 1981. This proved to be a smart move and BMB racked up enough in sales that it was able to open six retail stores.

The company went public in 1983 but then experienced difficulties the following year after a market downturn. BMB responded by discontinuing the retail side of its business to focus on its own hardware and software products.

Some websites have suggested that BMB went out of business as a result of litigation but this is not the case. BMB was involved in a landmark ruling in Canadian trademark law named BMB Compuscience Canada Ltd v Bramalea Ltd. and this appears to be the origin of this myth. The company continued into the ’90s before being acquired by Systems Xcellence Inc. in 1994 in a reverse takeover. The company later changed its name to SXC Health Solutions, and then Catamaran Corporation, before being acquired by UnitedHealth Group in 2015.


Illustration: Imaginet logo

BMB was not a games company; Sopwith was developed as a demo application for the Imaginet networking system, an early form of LAN that networked IBM PCs and Atari STs. David Clark has described Sopwith as something he hoped would attract attention at trade shows. A more serious application for Imaginet was an electronic mail system system called NetMail, which was later the subject of the lawsuit mentioned above.

The Imaginet system does not appear to have been particuarly successful and not much information seems to be available on it. One article about the system explains that it allowed multiple computers to share a floppy disk drive to exchange data, with the drives possibly being entirely virtual. From examination of the source code, Sopwith itself appears to have worked by having different players continually reading and writing from the same disk sector.

On the client computers the drive would appear as though it was just another floppy drive. This was the origin of the Imaginet name, the idea being that “you have to imagine that a network’s really there”. Marketing materials for Imaginet emphasized this “transparency” that allowed normal DOS software to interface with the network; this was probably a very important feature in the years before 1987 when MS-DOS 3.0 introduced native interfaces for networking.

BMB had previously developed a very similar network system to Imaginet for the Commodore PET called MUPET which had enjoyed some moderate success. As with Imaginet it allowed multiple computers to share a floppy drive. Much more is known about this system which may give some sense of how Imaginet worked:

The inspiration

Illustration: Sopwith Camel

The Sopwith Aviation Company was founded by aviation pioneer Thomas Sopwith in 1913. After World War I broke out, it became one of the main manufacturers of military planes for the war effort. This included the 1½ Strutter two seat general purpose biplane, and the Pup and Triplane fighter planes.

Technology advanced quickly over the course of the war and the Pup was quickly rendered obsolete; the Sopwith Camel F.1 was an evolution of the design that was faster, more manoeuvrable and more heavily armed. It acquired its (unofficial) name as a result of a metal fairing over the gun breeches that gave the appearance of a hump. While the game does not clarify which Sopwith plane is being flown, it is assumed to be a Camel, since it is one of the most famous planes of the war; certainly the most famous produced by the Sopwith Aviation Company.

Camel pilots shot down 1,294 enemy aircraft over the course of the war, more than any other aircraft. The plane gained a reputation for being agile but difficult to fly; many novice pilots crashed the plane on takeoff. 5,490 Sopwith Camel aircraft were produced. In popular culture the Camel is known for being the biplane flown by the protagonist in the Biggles series of novels, and by Snoopy in the Peanuts comic strip (in his imagined dogfights with “The Red Baron”).

Original DOS Sopwith versions

There are several MS-DOS versions of Sopwith which contain different features as the game was expanded and developed. Please note that other than the Author’s Edition, these versions are not open source.

  1 1.5 2 Network Edition Author’s Edition
Solid ground        
Speed depends on CPU      
Enemy planes drop bombs        
Oxen and birds    
Explosions leave debris    
Novice mode      
Missiles and starbursts      
Wounded planes      
Window “splats”      
Imaginet multiplayer  
640x200 “hi res” mode ✓ (-h)  
Async (serial line) multiplayer    
Joystick support  
Compiler Computer Innovations C CIC CIC Microsoft C MSC

Sopwith 1

The oldest version, released in 1984, was the original demo for the Imaginet networking system developed by BMB Compuscience of Canada. Its main distinguishing feature is the use of solid white ground, which was later replaced by a single line (to improve performance). To avoid having to redraw the screen, the “camera” only moves sometimes.

Speed is CPU-dependent, so the game runs too fast on machines faster than the original IBM XT unless a utility like MOSLO is used (or the number of cycles adjusted to a low number on emulators like DOSbox. As with later versions, this version supports running the game in 640x200 CGA “hi res” mono mode, but the command line argument to enable it is -h; this was changed to -w in later versions.

The musical theme to this version is Merrily We Roll Along better known as the theme song for the Warner Brothers Merry Melodies cartoon. However, the music doesn’t play on the title screen unless Sopwith is run with the -s command line parameter.

Multiplayer depends on the proprietary BMB drivers and Imaginet networking system and to my knowledge, no fans have ever been able to get it working.

A review was published of this version in the book “Free and user supported software for the IBM PC”; you can read it here.

Sopwith 1.5

I recently came across this version, which I’m calling Sopwith 1.5 since its development clearly sits between the better known Sopwith 1 and 2. In my opinion this is perhaps best described as a beta version of the later Sopwith 2 - it is unique in that computer planes drop bombs, a feature that never appeared in any other version and does not appear to work very well.

Solid ground has been replaced by a line at this point in development, and joystick support added. However, later changes are not yet present, like oxen and birds, or explosions leaving debris. It still runs at the speed of the CPU, like Sopwith 1, so the same slowdown techniques are needed to make it playable.

By this version the theme music has been changed to The U.S. Air Force (aka Wild Blue Yonder), the official song of the US Air Force. This music is used in Sopwith 2 and all future versions.

Sopwith 2

Perhaps the best-known of the DOS versions, this was a significant step forward over the original. Note that the name “Sopwith 2” is a fan invention to distinguish it from the older version, and the game does not describe it with that name.

In terms of gameplay the most immediately noticeable feature is the addition of oxen and birds to the game. More subtle changes include tweaks to how explosions work - debris is longer-lived and provides more of a hazard to the player. Speed is now CPU independent, the game supports IBM compatible joysticks, and serial line networking, although this latter feature is still unusable because it also requires a proprietary BMB driver.

Network Edition

Released by the author David L. Clark in the late ’90s, the main features are the addition of novice mode and wounded planes. Novice mode in particular is convenient since it makes it impossible to stall the plane, a common stumbling block for new players.

A controversial feature added in this release is guided missiles and starbursts (chaff/flares) which are presumably intended to make multiplayer more fun (they have to be enabled with the -x command line parameter). The missiles are dumb missiles when fired by the player but heat-seeking when fired by computer planes, making the single player experience almost impossible.

Some more subtle changes: oil tank explosions were made much smaller, bird strikes no longer result in an explosion, and computer planes avoid crashing into oxen.

A cute addition is that of window “splats”: bird strikes result in a splatted bird appearing on the screen, and getting hit by a bullet results in similar broken glass cracks. Perhaps the funniest of all occurs after flying through an ox: the entire screen turns pink from blood.

Drivers are available that can be used to play this version and the Author’s Edition over a serial line; see the download link below. These were originally posted by the user “per” on a thread on the VCFEd forums. These drivers apparently (?) do not work with Sopwith 2. A driver file is also included for the original BMB network hardware, but you are unlikely to be able to get this to work unless you have original BMB hardware. Under DOSbox you will need the DRVLOAD program to be able to load the drivers.

Author’s Edition

Largely identical to the Network Edition, but the original BMB networking has been removed. This was the basis for the source code release by David Clark.

The code was originally released in 2000 under a non-commercial license, but was later re-released under the GPL in 2003. There are some very minor differences between the two source releases. A GPL blurb was added to the program help text (as the GPL itself recommends doing), and the copyright year on the title screen was updated. The earlier release described itself as “Distribution Version” rather than “The Author’s Version”, presumably because Clark doesn’t want other people calling their versions by that name.