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Unfortunately, while Exec (the kernel) and DOS (the file system) were not really tied that hard to the architecture, Intuition (the GUI) was very tied to the ha

by spc476 12y ago

Unfortunately, while Exec (the kernel) and DOS (the file system) were not really tied that hard to the architecture, Intuition (the GUI) was very tied to the hardware. Change the video, and you have a new GUI to code for. Also, it may not have been all that possible to enhance the hardware from the given design [1]. [1] A bit-plane video architecture. For example, say the video is 256x256 (for simplicity) 1 bit color. That's 8 bits per pixel, 8K video buffer. What 2-bit color? Okay, the low bit of each pixel s in one 8K video buffer; the high bit of each pixel is in another 8K video buffer. Want 8 colors? Add another 1-bit 8K video buffer. Now you have one pixel spread across three bytes. Never mind that Intuition also allowed control access to the Copper [2] so you could also specify the screen resolution and color. You could split the screen (upper half, 320x100, dual play fields (three bit planes defining the background, three bit planes defining the foreground) with 32 colors, and the lower half 640x200 (interlaced) with four colors). You could also specify up to 8 hardware sprites. Yup, Intuition was very tied to the video hardware. [2] A special 3-instruction CPU to control the hardware registers based on the video beam position, allowing you to change the entire video setup virtually anywhere on the screen (any given scan line, within four pixels horizontally); colors, memory used for the video buffer, resolution, sprite locations. You could literally display all 12 bits of supported color on a single 1-bit video page by mucking with the register settings on a per-4-pixel basis using the Copper. It'd be a long Copper program, but the 68000 would be completely idle.

mtviewdave 12y ago
The Amiga 1000 could support a 640x400x4 bitplane 30fps interlaced display with its 16-bit path to memory at 7.14MHz. If you double the clock, and double the width of the data bus, then a 640x400x8 bitplane at 60fps becomes theoretically possible, which would have made it an easier sell for business (the need for a non-interlaced 640x400 mode was obvious quite early on) Obviously there's more to improving the graphics architecture than just improving the clock and data path. My point was that the easy benefits of Moore's law at that point would have substantial improvements possible, if Commodore was able and willing to make the attempt. "What amazing graphics thing are we going to do next?" was the question Commodore needed to be asking themselves in 1985, but it's clear they didn't. How much of that was due to money, and how much was due to corporate culture, is not clear to me. And WRT Intuition: it was tied to the hardware, but you overstate the case. Later Amigas had new graphics modes, and Intuition had support for 8 bitplanes from the beginning. I don't think 640x400x8 @ 60Hz was impossible, or even that difficult, in 1987, from an OS perspective. BTW, anyone else disappointed that there are no Amiga engineering alum who have discovered this thread?

by spc476 12y ago

mtviewdave 12y ago

The Amiga 1000 could support a 640x400x4 bitplane 30fps interlaced display with its 16-bit path to memory at 7.14MHz. If you double the clock, and double the width of the data bus, then a 640x400x8 bitplane at 60fps becomes theoretically possible, which would have made it an easier sell for business (the need for a non-interlaced 640x400 mode was obvious quite early on) Obviously there's more to improving the graphics architecture than just improving the clock and data path. My point was that the easy benefits of Moore's law at that point would have substantial improvements possible, if Commodore was able and willing to make the attempt. "What amazing graphics thing are we going to do next?" was the question Commodore needed to be asking themselves in 1985, but it's clear they didn't. How much of that was due to money, and how much was due to corporate culture, is not clear to me. And WRT Intuition: it was tied to the hardware, but you overstate the case. Later Amigas had new graphics modes, and Intuition had support for 8 bitplanes from the beginning. I don't think 640x400x8 @ 60Hz was impossible, or even that difficult, in 1987, from an OS perspective. BTW, anyone else disappointed that there are no Amiga engineering alum who have discovered this thread?