King's Quest IV was the first game that used Sierra's brand new engine: Sierra's Creative Interpreter (SCI). Before King's Quest IV, Sierra used the AGI engine which was introduced in 1984 with the release of King's Quest 1: Quest for the Crown. The AGI version (version 2.0) was co-produced and released with the SCI version for the presumably many customers who's computers did not meet the high hardware requirements of the new SCI engine. Customers that could not run the SCI version were able to send in the SCI version for an AGI replacement.
However, sales figures proved Sierra wrong and the AGI version was swiftly discontinued. Because of its rarity, the AGI version could be considered a collector's item.
SCI is said to have a higher resolution but in actuality only added dithering, which only gives the impression of higher resolution. Eventually, with the SCI1.1 interpreter, they included drivers that would work on older computers in the same game instead of developing an entirely separate version. All SCI1.1 games had an EGA 640x400 dither driver that worked with older hardware.
King's Quest IV: AGI (version 2.0)
King's Quest IV: SCI (version 1.006.004)
There are also many differences in the game itself:
- The AGI release contains three Easter eggs which are not included in any other release of King's Quest IV: the "Beam me", "rap kq" and pirate Easter eggs.
- Rosella does not lie down 'seeing stars' when falling from small heights.
- When advancing into the Dwarfs' bedroom, a Dwarf inexplicably appears and ousts Rosella from the house.
- When the Seven Dwarfs serve themselves, Rosella doesn't observe that the last dwarf takes two plates.
- The ocean sparkles from time to time
- Squirrels and bluebirds can be seen in the trees occasionally.
- Saliva drops from the whale's mouth
- The dolphin arrives at the south of the little island.
- The magic Hen does not walk on the Ogre's table, it stands still.
- Night does not fall as Rosella finishes her first 2 tasks. It falls real-time, when clock shows 9:00
- The artifacts she digs up from the graves don't appear in the holes
- Betty Cowden's ghost doesn't materialize after Rosella enters the room. It is already there.
- The tree is specifically called the Tree of Life.
- In Lolotte's Castle, Rosella can reenter the dungeon cell. In the SCI version the narration replies that Rosella is not eager to see her cell again, leaving the door closed.
Differences in SCI releases
There are also differences between the initial SCI release (version 1.000.111) and later SCI releases (which were also included in the collections). For example:
SCI, version 1.000.111
SCI, version 1.006.004
Like many backgrounds in the game, it's been very notably altered from the original release. In this case, it's especially noticeable, because the two trees in the foreground are now gone!
Also note that the tree branch in the upper left corner, as well as the trees in the far background, are now depicted in shadow instead of being fully colored. In the later versions of KQ4, the art was altered so that the day and night versions of scenes could share art resources, which resulted in changes like this one. The original version of the game had included separate backgrounds of each location for day and nighttime.
The first game ever with sound card support
Another main advantage of the SCI engine was the support for music cards. King's Quest IV was the first commercial entertainment product to support add-on music cards and synthesizers, such as the AdLib Music Card and Roland MT-32. Standard IBM PCs came equipped with a speaker capable of only simple beeps and tones, at a time when video-game consoles and competing personal computers (such as the Apple IIGS and Commodore Amiga) possessed far more sophisticated sound-generation hardware. Sierra's new SCI engine allowed the game designers to incorporate an orchestrated musical score along with more complex sound-effects, a previously unattainable feat. To ensure an immersible soundtrack, composer William Goldstein, known for several Hollywood soundtracks, was hired to write the game's musical score, totaling over 75 short music pieces.
