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Everything posted by Guybrush

  1. No they don't. If you really need scrolling, you can fake the bitmap mode with tile mode. Since you're only using 160x120, there should be no problems having enough different tiles.
  7. Why can't you use tiles for the shoreline?
  17. Yeah, it's really much better suited for assembly since you can simply test the MSB with BPL or BMI after loading.
  18. Your RLE format is somewhat hungry for memory space . I'd use a [RunLength], [Value] format where RunLength's MSB indicates whether it's followed by a single byte value that is repeated N times, or by N bytes that are only used once. So, a data stream that looks like ABCDDDDDDDEFGHIJJJJJJ would be stored as 3,A,B,C,135,D,5,E,F,G,H,I,134,J for a total of 14 values, while your format would be A,1,B,1,C,1,D,7,E,1,F,1,G,1,H,1,I,1,J,6 for a total of 20 values. The difference would be even greater if there are many non-repeated values. Of course, this could be extended to indicate, for instance, that what follows is a pattern of M values that should be repeated N times, by using a few bits of the RunLength byte.
  19. First of all, that chip uses SPI or I2C to communicate with the host computer. That means (in case of Commander X16) that you'd be spending most of your cycles bit-banging its control and data lines through one of the VIAs. I think you'd need something on the order of 100 cycles just to send one byte over. Since one frame (assuming the display is still working at 60Hz) has approx. 133,333 cycles, you'd probably be able to send whopping 1300 bytes during one frame. Maybe it could be faster but still nowhere near the simplicity and speed of writing to a VERA data port. Secondly, that chip works with display lists which themselves contain many different graphics primitives (and ones not so primitive): Essentially, you get something that performs anti-aliased blending of JPEG files and geometric primitives all on its own. That's not a video controller, that's a GPU. Think of it as a bastard child of Amiga's Copper and an early OpenGL accelerator. And I do think it's a bit over-the-top for this kind of computer.
  20. Since the expansion ports (at least to my understanding) have all 16 address lines and both the RDY and BE lines, you should be able to halt the CPU and take over the system, even going as far as replacing the 6502 with another CPU (e.g. a 65816) on your expansion card.
  21. In case of VIAs, YM-2151, VERA, the're internal to the chip. In case of $00 and $01, they're in separate components on the board, probably in the same bunch as the address decoding logic.
  22. Yeah, TGA is quite programmer-friendly, but many (most?) TGA files are written bottom to top, which means you'll probably have to reload VERA's address register for every line of the bitmap. I remember playing around with Turbo Pascal back in the 90's, writing a TGA image viewer for files created by POV-Ray and being quite surprised when the image finally showed up, only upside-down. Of course, I only had a faint idea what that thing they call the Internet was and you can imagine it was quite difficult obtaining file format specifications. Ahhhh, happy days
  23. Well, if you use PNG transparency, it should be relatively easy. Whether your sprite graphics correspond 1:1 to your collision mask is another matter. Suppose you're making a remake of Barbarian or International Karate... sometimes you need to allow some sprite overlap and not register it as a collision, e.g. hand-to-hand collision should be expected and not count as a hit. So, even though you could use sprite graphics to generate the collision mask automatically, there's plenty of situations where that's not practical.
  24. Well, for one, your article is written in such a manner that one might think the computer is already being sold, which it obviously isn't. In multiple places you refer to the computer in the present tense, where the future tense would definitely be more appropriate. Wikipedia's general notability guideline (to which the message refers) clearly states that the topic must have "significant coverage in reliable sources that are independent of the subject". This site (or the Facebook group) is definitely not independent of the subject. Since the computer hasn't been released yet, there really can't be any significant coverage in other reliable sources. Frankly, this message from the admins really doesn't surprise me, I expected something like this to happen since I've first seen the article, I'm only surprised by their expedience .
  25. Exactly, only the numbers are different (64 tiles vertically for 80×60 text mode, which means the tile map repeats every 512 pixels). You may be wondering why scrolling is supported up to 4096 pixels... it's because at the maximum tile map size (256) and maximum tile size (16 px), total size of the layer is 256 * 16 = 4096 pixels.
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