800 x 600 tile driver??

johnfl68

Has anyone had any luck making a 800 x 600 tile driver (or has this been done, and I just can't find it)?

I have had luck modifying vertical resolution in small increments to change to other resolutions, but as soon as I change horizontal, even by just one pixel, or 16 pixels, the monitors will no longer sync with anything.

Does anyone have any suggestions?

Thanks!

John

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Whistler: I want peace on earth and goodwill toward men.
Bernard Abbott: We are the United States Government! We don't do that sort of thing.
Sneakers (1992)

kwinn

Increasing horizontal resolution means either more pixels in the same time (higher pixel clock rate) or longer horizontal scan times (lower horizontal frequency). Increasing vertical resolution requires increasing the number of horizontal scan lines which means either more lines in the same time (higher horizontal frequency) or a longer vertical scan time (decreased vertical frequency). To avoid flicker the screen must be refreshed at a reasonably high rate (60hz typically), and that in turn will determine the horizontal and vertical scan frequencies for a specific resolution. The higher the resolution for a given refresh rate the higher the horizontal and vertical frequency. Your monitor must be able to lock on to those frequencies to display a stable image. Most monitors are now "multisync" units that will handle several resolutions (640x480, 800x600, 1024x768, 1280x1024) and refresh rates (60hz, 72hz, 75hz), but they do not handle "in between" rates well if at all.

johnfl68

Does anyone have any thoughts on this??

I took the 1024x768 tile driver, and changed it to 50 x 38 tiles, I modified the tile driver for 800x600 timings (with the exception for the pixel rate, which I have tried all the possible settings but I think it should be around 40):

hp = 800 'horizontal pixels
vp = 600 'vertical pixels
hf = 40 'horizontal front porch pixels
hs = 128 'horizontal sync pixels
hb = 88 'horizontal back porch pixels
vf = 1 'vertical front porch lines
vs = 4 'vertical sync lines
vb = 23 'vertical back porch lines
pr = 40 'pixel rate in MHz at 80MHz system clock (5MHz granularity)

I have tried on a CRT and the closest I got was what looks like a rolling set of patterns with about a 2 second long repeating cycle, as if it is taking 2 seconds to display the image, but that doesn't make any sense (to me) as it is a smaller image than the 1024x768 was.

I am sure there is some part of this that I am missing, but I can't think of what I need to try changing that I haven't already.

Thanks again.

John

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Whistler: I want peace on earth and goodwill toward men.
Bernard Abbott: We are the United States Government! We don't do that sort of thing.
Sneakers (1992)