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Thank you :) I am considering doing a series of blog posts, I don't know how often I could write them or if I could keep them going, but I will try.
I'm not big in social media and I have never written any posts or anything like before this one, which is weird, I'll admit it, so all this is kind of new, but I think I'll give it go. Old systems used line-buffers like the Neo Geo or no buffers like the NES, for example.
So yeah, going with a frame-buffered approach was definitely easier, but this was not the only reason I chose this way.
I had a lot of restrictions, I was learning a lot of stuff, I didn't know how to work with FPGAs and I stuck with DIP package ICs that I could put on breadboards and experiment. And that's why I picked the AVR microcontrollers, which are awesome but have their disavantages. They have good performance (20Mhz), but not many pins and I had to bit-bang things like external RAM access (actually the PPU accesses 3 RAMs with only 32 IO pins available), which meant that it takes "some time" to access external memory.
That's why I chose 2 microcontrollers for video instead of just one, one of them could take "all the time in the world" (one frame) to fetch information and write a frame to the frame buffer while the other would generate the video signal and dump the a frame to the TV. Connecting the two, I felt a double buffer was better. I definitely would have preferred doing a more "traditional" non-buffered render system, but this was the solution I found with what I had to work with. I hope serves as a good explanation and maybe I'll get to explain these details better in another post :). |