One reason was that originally the only way to access display memory in Chip8 was to write 1802 MLS code. I did that a lot. If the purpose of those routines were known, then the functionality could maybe be emulated, but there's little point in emulating the actual 1802 subroutines since they are surely hardware dependent.
This was one of my concerns in writing my emulator MyChip8 in which there are two kinds of memory space relating to the display: that used by the interpreter, and that used by the library OpenGL code that I used to create the display animation. (Qt handles page swapping automatically for a very smooth result.) The interpreter's display memory is simply a 64x32 byte array, and therefore already incompatible with the original Cosmac bitmap display memory. But you could access it in the C++ interpreter code for a special purpose.
For what it's worth, MyChip8 emulator, which I wrote in C++ using Qt OpenGL graphics for the display is relatively new. I use Octo to compile and MyChip8 to run. The source code and building instructions for the emulator is on GitHub at: https://github.com/TomSwan/mychip8
First, let me thank you here, Tobias, for contacting me and making me aware of OctoJam. The enthusiasm here is awesome and I hope that I can contribute something worthwhile (or maybe just fun) to the mix! In recent months I wrote a Chip-8 interpreter "MyChip8" in Qt and C++ and, that done, I am now revising "Surround," from Pips for VIPS I. Reading that code and text has really taken me back to my origins! The original code runs, but not perfectly (perhaps due to its MLS calls, which I had to strip out of course). I considered perhaps fixing the bug, but it's not really in Octo; it's just the Chip8 byte codes in 0xff format. I wanted to write a new game in Octo, so that's what I'm doing for the Jam. The revised game, which is close to working, is called "Snake Surround" (I see there is a Snake entry already and it's really good! Mine is similar but different -- but the more the merrier, right?!) Cheers to all. -- Tom
