Alright! King’s Quest IV came out in both a SCI and AGI version. Unfortunately, KQIV used AGI3 and SCI0. Personally, I thought AGI3 was a bad idea. Everything was name coded. Anyway…
King’s Quest IV AGI was released only on 3.5 inch floppies for the AppleII series. Which leads me to believe that it was never released for the AppleIIe/c/+. Plus, the boot disk for KQIV used ProDOS16 which would never run on a AppleIIe/c/+. So, this leads me to beleive that the old AppleIIe/c/+ could not handle the requirements of AGI3. And, for some reason, the staff at Sierra thought that the AppleIIGS could not handle SCI0. Personally, from my programming experiences on the IIGS, I know for a fact that it could run SCI0, 0.1 and 1.0. I tried getting the 16-bit SCIW and SCI32 to run on my old GS, but it couldn’t handle it.
Yes, I wrote a SCI emulator on my GS and after upgrading the processor and memory, it handled KQIV, SQIV and SQ5 quite beautifully. Unfortunately, I no longer know where the emulator cd is anymore.