Wednesday, January 17, 2024

King's Quest IV - The First True PC Compatible Game

KQ4 Box, courtesy of MobyGames

When we think of PC Compatible games, thoughts of freedom may pop into one's mind. Intel, nVidia, AMD, gamers generally have a choice of which hardware to use in their systems. PC games have been, generally speaking, not tied to any particular manufacturer's hardware. Competition within the PC hardware market allowed consumers the luxury of choice. In the 1990s and onwards your motherboard could have been made by one manufacturer, your graphics card by another and so on and you could get a really good gaming experience. But this was not always the case, PC compatible games of the 1980s were often seen as lacking compared to other computers and generic PCs were content to clone rather than innovate. This all began to change in 1988 when King's Quest IV was released. In this blog article I will briefly summarize the evolution of PC gaming hardware and then discuss how KQ4 opened up PC gaming into what would eventually become the default non-console paradigm of how to play video games.

Gaming Hardware Evolution on the IBM PCs and Compatibles from 1981-1987, the Short Version

The IBM PC, released in August of 1981, could play games but IBM did not emphasize its game playing capabilities. I have discussed the specifications and abilities of the IBM PC at length in many previous blog entries, in short it was just a step up from the Apple II+. It's 4-color 320x200 Color Graphics Adapter and 1-voice PC Speaker sound could not compete with the specialized graphics and sound chips of the Atari home computers, the Commodore 64 or the TI-99/4A. Using a joystick required purchasing an expansion card just for that purpose.

To entice consumers to buy an IBM Personal Computer with a lower cost option, IBM released the IBM PCjr. in January, 1984. To address the PC's shortcomings in the entertainment software market segment the PCjr. offered a pair of built-in joystick ports and cartridge slots, improved 16-color graphics at 160x200 and 320x200 pixel resolutions and a 4-voice sound chip. For reasons which are well-known, the PCjr. was not a success but the Tandy 1000, which cloned the PCjr.'s graphics and sound capabilities but had better PC software and hardware compatibility was the dominant line of affordable PC compatibles in the mid-to-late 1980s. 

The IBM PC, PC/XT, PCjr. and Tandy 1000 used the Intel 8088 CPU running at 4.77MHz. In 1984 IBM released its IBM AT computer, which used a 6MHz and later an 8MHz Intel 80286 CPU which ran software three to four times faster than the 8088 machines. The Tandy 1000 EX, HX and SX (1986-87) came with 7.16MHz 8088s and the 1987 1000 TX came with an 8MHz 80826.  IBM also released the Enhanced Graphics Adapter with support for 320x200 and 640x200 16-color graphics. With a special monitor and a RAM expansion it could display 640x350 graphics with 16 colors from a palette of 64 colors. The IBM PC/XT and Tandy 1000 HD came with 10MiB hard disk drives. The IBM AT used 20MiB and 30MiB drives. Hard drives of similar sizes could be installed in most machines that did not come with hard drives. As the prices for 286, EGA and Hard Drive systems were very expensive at first, it took a few years before the costs came down sufficiently for support for these features became supported in IBM PC compatible games.

In April of 1987 IBM had discontinued its PC line of personal computers in favor of its PS/2 line. The higher end PS/2 computers used a different expansion bus architecture known as MCA and introduced the VGA graphics standard. This standard could show 256-colors on screen at the now-standard 320x200 resolution but required a new high definition analog color monitor. The lower end ISA-bus based PS/2 computers (Models 25 and 30) received the MCGA graphics adapter, which could also show most of the resolutions of VGA, but unlike VGA, MCGA is not backwards compatible with EGA. Due to VGA's high cost it took a few years before a majority of games began to support it, like EGA before it.

KQ4 Title Screen SCI (Left) and AGI (Right)

Sierra's Adventure Game Interpreter

In 1983-84, Sierra On-line had bet heavily on the PCjr.'s success by developing King's Quest for the system. King's Quest was designed to take advantage of the 16-color graphics and 4-voice sound of the PCjr. and fit into the 128KiB of RAM that an off-the-shelf PCjr. had. Unfortunately that bet did not pay off as the PCjr'.s software and hardware sales were slower than anticipated. Sierra quickly ported the game to the IBM PC in order to survive as a company, but the PC port did not have the same level of graphics and much weaker sound. When the Tandy 1000 proved popular and Tandy was looking for software for its new computer, Sierra was happy to provide it, quickly porting King's Quest to the new machine and forming a mutually beneficial partnership with Tandy/Radio Shack.

From 1985-1987 Sierra focused mainly on the PC market and specifically on the Tandy 1000s. By King's Quest II it had developed a game engine, the Adventure Game Interpreter, which was designed to run best on Tandy 1000s. (The original booter versions of King's Quest used a scripting language called the Game Adaptation Language, so while King's Quest and King's Quest II look similar to the player, underneath the surface they are very different.) The AGI game engine made it much easier to develop 3-D adventure-style games than creating a game from scratch every time. The engine was so successful that Sierra would use it for eleven original games and three games ported from other engines.

Post-Title Credits

At first, the AGI games (King's Quest II, The Black Cauldron) were PC booters: they did not use DOS, only ran off floppy drives, required disk swapping and only supported Tandy/PCjr. 16-color graphics, CGA 4-color RGB graphics, CGA 16-color composite graphics, Tandy/PCjr. 4-voice sound or PC Speaker sound. Then in late 1986 Sierra's AGI games began supporting 16-color EGA graphics, then required DOS and could be installed on a hard drive and eventually supported MCGA 16-color and monochrome Hercules Graphics.

Opening Cinematic Sample 1

By 1987, the AGI engine and its chunky 160x200 pixel graphics were looking increasingly dated, especially in comparison to the Commodore Amiga and its 32-color graphics and 4-channel digital audio mixing capabilities. Defender of the Crown on the Amiga or even the Atari ST made most PC games look and sound primitive. The AGI engine had made significant strides in bringing equality to PC owners regardless of the manufacturer, but it still favored Tandy for the sound chip. The AGI engine only supported keyboard and joystick input on PC even though it offered mouse support on non-PC platforms.

The Sierra Creative Interpreter and King's Quest IV

Sierra realized its AGI engine games could no longer compete and that PC hardware was no longer at the level it was in 1981 or 1984, so in 1987-1988 it developed the Sierra Creative Interpreter to replace AGI as its adventure game development platform.  The new interpreter had more advanced scripting, support for multiple fonts and could accommodate graphics, sound and input drivers. The first game which supported the SCI engine was King's Quest IV, released in September of 1988. KQ4 was the first PC-compatible game which brought everything together, graphics, sound, input, performance and storage, which we can expect of a PC Compatible game.

The game was groundbreaking in its presentation, it had a lengthy cinematic intro, post-title credits with a cinema-style presentation, a day & night cycle, a popup text parser, multiple character sprite sizes and a lengthy musical score. Otherwise its gameplay was little different from other Sierra games which came before it. Puzzle solutions can be logical or obtuse, stairs and mountain paths can be deadly to navigate, deadly enemies can be randomly encountered on certain screens, dead-end situations are easy to realize and the land of Tamir wraps around from north to south.

Opening Cinematic Sample 2

AGI had used an effective 160x200 pixel resolution for its graphics but SCI supported 320x200 pixel graphics. The 320x200 pixel resolution was still constrained by a 16-color limitation, but it made KQ4's graphics significantly more competitive with other 16/32 home computers. More importantly, you did not need an IBM or Tandy machine to experience the ideal resolution and color graphics. Any Tandy 1000 and any PC-compatible with EGA, MCGA or VGA graphics would show KQ4 at its best. EGA clone cards and computers with built-in EGA graphics had become affordable by 1988. KQ4 did have graphics drivers for CGA and Hercules with compromises due to their limited graphic capabilities. Eventually even the IBM PCjr. and the Amstrad PC-1512 16-color mode were supported in KQ4 in 16-color mode.

Whately Manor - Early SCI Versions (Left) & Late SCI Versions (Right)

Input devices were not ignored. Keyboard input was required because KQ4 used a text parser to interact with the world. Character movement could be accomplished via cursor keys or the number pad, a joystick or a mouse. While the mouse support in KQ4 was extremely basic, it eventually improved in later games to allow the right mouse button to function as a "look at object (clicked on)" command and would with the 256-color SCI games become the primary means of controlling those games with the introduction of the icon-based interactive system.

Sound of course is what KQ4 is known for, it is the first IBM PC compatible game known to support a sound card. Sierra contacted Ad Lib, IBM and Roland to find affordable sound options for their game with its full music score. IBM began selling its Music Feature Card in 1987, as had Ad Lib with its Music Synthesizer Card. The IBM MFC provided a MIDI interface for communication with MIDI devices such as sound modules and keyboards and a 4-operator FM Synthesis stereo audio source with 240-predefined sounds and memory for 96 user-created patches. The Ad Lib MSC used a 2-operator 9-channel FM Synthesis monoaural audio source programmed via register writes. Roland had a capable external MIDI interface called the MPU-401 which it had been selling for several years prior to 1988 and which had an interface card for PC compatibles. Roland also began selling the MT-32 in 1987, a 32-polyphony Multi-timbral 9-channel MIDI sound module relying on a combination of sampled sounds and programmable sound tones called LA Synthesis with a reverb unit.

Starting Point - SCI (Left) and AGI (Right)

Sierra chose to support these three sound standards in KQ4. The Ad Lib MSC proved to be the most popular of the three devices because at $195 it was almost 1/3 of the price of the Roland MT-32 ($550) and IBM MFC ($600) options. Sierra's composers focused on the Roland MT-32 and would bring out the best of the module, including the use of custom instrument patches, in later games. KQ4 still supported Tandy 1000 4-voice and PC Speaker-only systems. The addition of these sound options allowed the PC Compatibles to compete favorably with the Amiga, Atari ST and Apple IIGS. Sierra emphasized the features of these sound cards heavily in its advertising, noting it had hired professional TV composer William Goldstein to compose the score for KQ4. Sierra also released a demo cassette titled "Live from the Sierra Lounge" featuring recordings with the Adlib and MT-32 of several songs from its upcoming games.

One of Nine, courtesy of MobyGames

The size of KQ4 is another factor which favored the PC. KQ4 came as nine 360K 5.25" floppy disks or four 720K 3.5" floppy disks. Most "epic" home computer games at this time required no more than four 5.25" disks or two 3.5" disks. The PC platform had supported hard disks of increasing sizes since DOS 2.0 and there were many semi-affordable options for adding a hard disk to a computer which came without one. KQ4 required 2.5MiB of hard drive space for a full install, but the need for redundant data on disks to facilitate disk swapping made for more disks than was strictly required by the full game size. While many early KQ4 players endured disk swapping and loading, undoubtedly games like KQ4 made them think more seriously about buying a hard drive. Sierra would eventually cut down the number of 5.25" disks required from nine to eight by simplifying and removing certain graphic elements in later versions of KQ4. 720K disks reduced the disk swapping burden considerably but 720K disks were still relatively new in the PC world and many PCs would need to have a 3.5" disk drive added to them to use 720K disks. Sierra was forward thinking by including both types of disks in most of its games from 1987-1990.

Only four disks, but 720K disks are read at the speed of 360K disks, courtesy of MobyGames

KQ4 was one of the first games to be completely installable to the hard drive. Once you had finished installing the game, you could put the disks back in the box and never have to insert them into the system again. Many other PC games, even if they required DOS or were hard drive installable, relied on a copy protected key disk to inserted into the drive when the game was loaded so the game could verify that it was a legitimate copy. KQ4 was one of the first games with manual-based copy protection, which allowed publishers to maintain a modicum of protection for their games while decreasing the inconvenience of trying to play the game and accomplish more productive tasks around the same time.

Finally, a word should be given about performance. KQ4 was developed on 286 and 386 computers and ran rather sluggish on most 8088, V20 and 8086 machines. This is especially true with the earlier nine-disk versions. Sierra also released an AGI version of KQ4 which would run better on the older systems. This version conformed to the AGI engine's limitations, so Tandy sound was the best sound it could play and mouse support was not included. Apparently people prioritized graphics and sound over performance as the AGI version of KQ4 did not sell well and Sierra did not convert another game from SCI to AGI. 

Cupid's Bath - Early SCI (Left) and Late SCI (Right)

It should be observed that KQ4 required 512KiB of RAM in its SCI version, compared to 256KiB for its AGI version. The RAM requirement required many systems to have upgraded their RAM just to play the SCI version. The general Conventional Memory limit was 640KiB of RAM and games would soon want ever more RAM and require more advanced CPUs to access that RAM.

Thus we have a game with ideal graphics and sound options which was available to just about every PC owner, not just IBM and Tandy 1000 users. The full or ideal KQ4 experience was harder to achieve on other personal computers. The Amiga port had only 4-voice digitized sound support, MIDI interfaces were not yet a thing on that platform at the time. The Atari ST had a built-in MIDI interface and KQ4 supported it, but if you could not afford an MT-32 you were stuck with the 3-voice music that sounds like the Tandy 1000 sound chip. (In other words, there was no lower cost sound option like an Adlib for the ST). Apple IIgs owners got AGI-quality graphics but the sound was far superior to the 4-voice Tandy sound in the PC AGI version.

It could be remarked that other games which only supported RGBI CGA and PC Speaker leveled the playing field as every PC user could enjoy those games regardless of system manufacturer and there were still many of those games being made even in 1987-88. KQ4 was arguably the first PC game that gave people substantial reasons to upgrade their systems and their components.

Meeting Lolotte - SCI (Left) & AGI (Right)

With KQ4 had a game which was epic not just in size but in scope. Sound card support would follow in other Sierra games and from other companies later that year. Sound card support was now the standard going forward and the PC games market would start growing rapidly from KQ4 onward. The Amiga's advantage in graphics disappeared once 256 color VGA graphics became standard in computer games by late 1990 and the Sound Blaster addressed much of the PC's deficiencies in digital sound relative to the Amiga when it was released in late 1989. 


  1. Random aside... have you seen a source for PC sales in the 80s? I always wondered what fraction of the market was captured by Tandy. I noticed by 1987 most games were supporting 16 color graphics on the Tandy, which were so much nicer than the 4 color CGA graphics.

  2. Once again amazing write up. I’ve played through both versions of Kqiv as I wanted to get the experience in the pcjr.

    I have a totally unrelated question. Did you ever post on a forum that you’d played a homebrew of Pac-Man that was in Tate mode? Similar to the donkey Kong Tate. If so do you have any information or is there anyone that has a playable beta for it? Thanks you.

    1. The only thing I can think of is Pac-PC II and Ms.-Pac PC, which do support unusual modes.

  3. were tandy or ega analog or digital video

    1. Digital video intended to be displayed on an analog monitor.

    2. so CM11 and CM5 were analog monitors, but only displayed 16 colors? could EGA monitors display all 64 colors

    3. I should clarify, monitors for CGA and Tandy like the CM-5 and CM-11 receive pixel color information as 4-bit digital pixel values from the video cable. EGA monitors can receive 4-bit or 6-bit digital pixel values. As these displays are CRTs, they are inherently analog but have a DAC inside the monitor to translate the digital values into analog voltage levels for the CRT guns.

    4. very interesting. i owned a Tandy 1000sx back in the day. So the Color Computer 3 also had a DAC that had 6 bit digital pixel values since it had 64 colors? and the Atari ST had 8 bit and 512 colors?

    5. The CoCo3 uses composite video out and for RGB analog video out.
      The Atari ST uses analog voltage values on its proprietary video connector. 512 colors would require 9 bits/pins which were probably deemed too expensive.

  4. what was the last kq and sierra games for Tandy 1000 16 color ? were there any sierra that used TGA2?

    1. The last King's Quest game that supported Tandy color is King's Quest V's 16-color release. Other 16-color versions, SQ4, SQ1SCI, LSL1SCI, PQ3, CotL, LSL5, MUFT would see the end of Sierra's support for Tandy Graphics. Sierra never supported TGA2.

    2. thanks. whats the best tandy 1000 16 color games?

  5. Another great write-up, GH. I remember being gobsmacked by KQ4 when it came out. Even with the PC speaker, it was a treat on my 286 with EGA and a hard drive. My XT owning friends who had to play on RGB CGA from floppy were not quite so lucky. Later adding an AdLib card took the game to a whole new level. And over a decade later I finally got my hands on a real MT-32 and that again made a world of difference. The older SCI releases on nine 360K disks did look a lot better than the later eight disk ones. Especially for the night scenes (which on the later releases seemed to barely change anything but the colour of the sky)

  6. could tandy 1000 16 color 320 by 200 be combined to create new color ? some tandy 1000 on youtube have new color beyond cga

  7. I appreciate the irony about needing to upgrade RAM to play this game. I had a Tandy 1000 SL with only 384K of RAM (effectively less that which was used for video). Someone gave me this game, but I could not actually play it. :-( I was so very disappointed.

  8. I remember seeing the AGI release on my friend’s IBM PC back in 1989, which involved a lot of waiting and disk swapping. By 1990 they had upgraded to a newer PC with a hard drive and Adlib card. Wow, was I blown away by seeing KQIV (SCI version) in almost its full glory (I would not get to hear the MT-32 tracks until well into the DOSBox and Munt era). In fact I’d say this one game was responsible for instilling in me a mild obsession with DOS games to this day. I “suffered” through owning an Amstrad ZX Spectrum 2+ and then the family took the Macintosh route. That, ironically, gave me an early career in niche IT support, yet I always hankered for the IBM PC games that I could enjoy in small doses at friends’ houses. So for me, it did all start with King’s Quest IV.