King's Quest 4 - Did you know they replaced background pictures??

[lance.ewing]

I get an error trying to run it in scummvm: "WARNING: AgiLoader_A2: disk 5 not found!"
Do you have a copy which scummvm can run?

I assume we have the same copy, as my one also doesn't work in scummvm. It does run in the Apple II emulator I'm using though (JACE).

[pmkelly]

Jeff Stephenson discusses how he ported the AGI interpreter to the Apple IIe at 55:00 in the following interview:

https://youtu.be/K3s0nW1FBN8?si=0iYqh4iMUEm8Vnkz&t=3300

[lance.ewing]

Yeah, I've listened to that one a few times over the past couple of years. It's great, especially the early stuff about the King's Quest project.

The Apple IIe was supposedly released at the start of 1983, when the King's Quest IBM PCJR project was in its early days. Sierra had obviously created a lot of Apple II games before that, but it would have been the older models. The Apple II+ supported up to 64K, which would have ruled it out, but with the IIe supporting more memory, it opened the door to Jeff trying to squeeze it in. It is interesting what he mentions about the first 256 bytes of memory. I don't know much about the Apple IIe yet but I plan to one day disassemble the 6502 code for the Apple IIe AGI interpreter to see how it works, which would be a first step towards potentially writing something for another 6502 based machine. Some sort of similar memory bank switching mechanism would need to be used, as the standard 6502 can only address 64K.

[cosmicr]

I started writing a 65c02 port of the AGI engine for the modern retro computer the Commander X16. It uses 512k banked ram in addition to the main 64k. So far memory hasn't been much of an issue. It does need careful management though. The hardest parts are dealing with the animation subsystems (ie views, priority, and buffering). The CX16 has a decent graphics card - the VERA with 128k of VRAM which helps.

Program code is about 30kb (give or take). That includes look up tables etc.

Attached is a gif of it loading Kings Quest 2 - you can see the glitchy view for the intro which is what I'm working on now. Loading is slow, but everything else is acceptable. It's slightly slower than say a Tandy 1000.

There's another guy making one in C for the CX16 which is a lot further along, but I'm not sure if it's still progressing. My idea was that if I could get it working on the CX16, then other 6502 systems would be worth a look. Even the Commodore 64 might be feasible, and with a lot of blood sweat and tears the NES might even be possible (with a few custom mappers).