1 = VGA Output Example Comparison = 2 3 In investigating different techniques, the following observations have been 4 made about the behaviour of the different VGA examples: 5 6 {{{#!table 7 || DMA Channels || Horizontal Resolution || Picture Stability 8 || Pixel Consistency || Scrolling Operational 9 == 10 vga || 1 || High || No || No || Yes 11 == 12 vga-cpu || 0 || High || Yes || Yes || Yes 13 == 14 vga-dual || 2 || High || No || No || No 15 == 16 vga-pmp || 1 || High || No || No || Yes 17 == 18 vga-timer || 2 || Low || Yes || Yes || Yes 19 }}} 20 21 Here, picture stability is assessed with the CPU accessing RAM. In general, 22 all of the approaches can provide stable pictures with limited RAM access 23 loading. However, under load, the picture will stretch and ripple for all 24 examples where picture stability is given as "No". 25 26 It should be noted that the vga-timer example employs two DMA channels, but 27 this is only to maximise horizontal resolution. With a single channel, 28 horizontal resolution is diminished still further in comparison to the other 29 examples. 30 31 It would appear that two most viable approaches are the vga-cpu and vga-timer, 32 if only because they produce consistently-sized pixels, retain picture 33 stability under load, and provide operational horizontal scrolling. These 34 approaches provide a tradeoff between performance (vga-timer being faster) and 35 resolution (vga-cpu being better).