Driven for Apple IIe

Details

Videos

System Requirements

• An Apple IIe with 128k RAM and Mockingboard
• It will not work on a IIc or IIgs currently as the Apple IIe VBLANK is hard-coded, if I have time I'll see about getting that to work

Downloads

Disk Images

• This is version 1.0 (15 November 2024) driven.dsk (140k)
  
• If you don't have real hardware it should work in emulators. Applewin (be sure to enable mockingboard sound support) and MAME both tested.
• Try it on the in-browser emulator at archive.org: (eventually, things haven't been the same there since the compromise [and I made a mistake in the metadata when uploading and it won't let me fix it])

Source

• You can find it in the full git repository here: You'll need cc65 to build it.
  https://github.com/deater/dos33fsprogs/demos/driven

Mini-faq

• Q. Why is there a glitch after the maglev ride?
  
  A. On an Apple IIe with 128k of RAM anything more than 48k requires obscure bank switching. Some of the memory regions (particularly parts in the "language card" especially in AUX memory) are extremely difficult to access when playing interrupt-driven Mockingboard music. So I ran out of room to stash code and have to briefly pause as I load from disk.
  
  It in theory might be possible to fix this. To access this memory though you have to on-the-fly switch your execution from one bank to another, including handing off the zero page and stack to alternate versions. As you can imagine you have to take special care for interrupts (maybe break up your copy routine into sub-50Hz chunks?). There's also at least one Apple II platform that "helpfully" switches around the banking for you on an interrupt which makes things exciting.
  
  
• Q. Who is dancing at the bottom of the credits?
  
  A. It's supposed to be Atrus on guitar, accompanied by Catherine and a Moiety soldier. It's really hard to get nice hi-res multi-color sprites on Apple II due to all the aliasing issues. You might notice the guitar sprite is based on Rather Dashing from the end of the "Peasant's Quest" game, you can see an early prototype of this credit scene here: Peasant Band
  
  
• Q. The one scene of World 233 is amazing. Why aren't all the graphics like that?
  
  A. That is a screen grab from the 2024 demake converted with the iipix tool to double-hires mode. This mode does look amazing (it's 140x192 16 colors) but the pictures are large (that one is 9k ZX02 compressed) so there isn't room to do have all images in that mode.
  
  
• Q. Those are some nice wipe effects.
  
  A. They are from the Total Replay collection by 4am and qkumba. It was a bit of a pain converting them to ca65 as well as de-macroing them to better fit in this demo.
  
  
• Q. Are you accelerating the disk loads? It loaded fast!
  
  A. The Apple II disk is a remarkable bit of Woz engineering. Coupled with qkumba fast disk code it leaves other alternatives like the Commodore 1541 in the dust.
  
  
• Q. Why does the music sound muddled?
  
  A. We've done a lot of research on this, including getting some chips decapped. It turns out modern Mockingboard replicas use AY-3-8913 variants of the chip, which sound worse than AY-3-8910 for some reason (we've verified the chips are actually different at the silicon level). Also the Mockingboard has low pass filters on the output which messes with some chiptune effects.
  
  French Touch has been investigating it, it might be possible to make helper circuitboards to get better chiptune output on Apple II.
  
  

Code Notes

Overall Framework

Effects summary

Opening	DNI numbering. Original inspiration for this demo. I have a variant that has plasma and sine scrolling but couldn't get it to easily work in the framework. Also, in the end, it didn't fit the vibe on the intro. Now we're just using it to count up as the files are loaded from disk (some to AUX memory).
Intro	Steffest made this logo and animation. It was tricky to do the full animation in a small amount of code. I did manage to get it to work and it's nothing overly exciting, mostly just software sprites and copying from Page2.
Atrus Scene	This is a 2-pixel wide horizontal scroll, which is really hard on Apple II. Apple II has no hardware scrolling, and the bitmap for hi-res mode has pixels in 2 bit chunks but the values are spread out so you have 7 pixels spread across two bytes, with palette bits in the way, and the bits are ordered MSB first. I tried a few ways but in the end this is an optimized version of the horizontal scroll code from my Second Reality port which uses table lookups. You can't really tell but it's a multi-color font, I meant to use something fancier but making a nice multi-color font is a huge task in and of itself (especially with Apple II hgr aliasing rules). It is jumpier than I'd like, I think part of that is the 50Hz of the music interrupt interacting poorly with the 60Hz of the VBLANK wait.
Maglev Movie	Lo-res hand-rotoscoped movie, ZX02 compressed. This is from the Riven demake.
Various Scenes plus wipes	As said before, wipes are from Total Replay. Some of the graphics are auto-converted with ii-pix, some are hand converted by me with the GIMP. I have various methods of hand-converting them and stick with the one that looks best to me, but it does mean the styles clash a bit. The falling image at the end is custom artwork by Steffest.
Credits	New, optimized vertical scroll code. It's a huge unrolled loop, as Apple II doesn't have scroll hardware. Had some fun with sprites going along with it.

Development Notes