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So I was reading the Stella Mailing List (I subscribe but never really post) and one person brought up the idea of BankDraw - A method of quickly updating sprites on the screen. The two other commonly used routines are SkipDraw and SwitchDraw. SwitchDraw being the faster of the two iirc. BankDraw is a little faster than those, but at the cost of space in rom to hold a mask table of zeros/ones/zeros. In a 2600 kernel, every cpu cycle counts. But generally so does every byte of ROM. With bankswitching techniques to increase the ROM size, however, you can step back and decide if you can afford the bytes for the mask table.
The inspiration behind BankDraw was how zones were set up on the Atari 7800, and thinking about it I can understand the connection. BankDraw also mimics the 7800's Holey DMA mode somewhat. So with my little 2600 project I'm slowly trying to work on (The upcoming move hopefully this weekend is distracting me obviously) I thought I'd look into how I could set up BankDraw. Everything else aside, I find it easier to understand than Skip or SwitchDraw so. ^_^; Long story short, I'm now pondering what kind of kernel I'll have to write to implement BankDraw efficiently for either 8 or 16 scan line zones. 8-line zones would save space on small sprites, but would likely require more variables in ram to display larger sprites. 16-line zones are the opposite. Save on potential ram use while needing to pad smaller sprites in rom with zero-bytes.
I can't seem to focus on it too much. Perhaps after I move and get settled in at the new place. x_x
The inspiration behind BankDraw was how zones were set up on the Atari 7800, and thinking about it I can understand the connection. BankDraw also mimics the 7800's Holey DMA mode somewhat. So with my little 2600 project I'm slowly trying to work on (The upcoming move hopefully this weekend is distracting me obviously) I thought I'd look into how I could set up BankDraw. Everything else aside, I find it easier to understand than Skip or SwitchDraw so. ^_^; Long story short, I'm now pondering what kind of kernel I'll have to write to implement BankDraw efficiently for either 8 or 16 scan line zones. 8-line zones would save space on small sprites, but would likely require more variables in ram to display larger sprites. 16-line zones are the opposite. Save on potential ram use while needing to pad smaller sprites in rom with zero-bytes.
I can't seem to focus on it too much. Perhaps after I move and get settled in at the new place. x_x
