To multisync monitor: Output of my converter goes to multisync switcher with 4 inputs and one output. Switcher supports up to 4K, screenshot is from device which has limit 1920x1080i/p. Converter normally outputs 1280x768, but this mode even forces 1360x768 - this look crazy - overloads maximum? Me personally I like VDC and want to break all written standards. Currently by Torsten (tokra) we can use 800x600 or 600x800 (H limit is 'cause VDC RAM size) - so, stable picture is up to 800H and 800V. Commodore 900 had to have 1024x800 - vertical limit is reached, even in graphic mode. If we can theoretically calculating 1024H can use max. 512V for VDC RAM limit...fits to RAM exactly Sadly, I don't understand how could VDC 8563 in C900 addressing 128K RAM, even when was C900 project cancelled, why that version disappeared... But finally - reach 1280H and maybe 400V can be compared with VIC-III in C65...it's 1280x400 in 4 colors, but graphic mode, but I don't know really, I mean that text and graphic variability is in VIC-III fixed to few modes instead VDC high variability. Miro
Commodore 64 was great, Commodore 128 is bigger, better, faster and more powerful... Commodore 65 was almost here, but C256 is coming and it will be earthquake...
Thanks, Tokra, for doing the math for us! (regarding VGA) I like your post where you spell out the "Horizontal-Total" value for both NTSC and PAL, and then give your best value for "VGA compatible". Great work, thanks for sharing. Those values were for the 8x2 video mode, and you noted it was essentially "impossible" to get true VGA compliance due to the 8-bit limitation...
And you also gave us a "pretty close" value for 8x3 color mode: 172 (for register 4?) and 2 (for register 5?), which according to your post gives (172+1)*3+2 = 521 lines (about 59.98 Hz). So thanks again for sharing your research!
But, is 521 lines standard for VGA? I thought it was 480? If VGA is trying to give 480 displayable lines, is the actual total suppose to be 525 like NTSC? I'm not a VGA expert, so that's why I'm asking. I do know NTSC should have 525 lines total (not all visible). So just curious is you think 521 lines is perfect for VGA, or maybe there was a mistake (...should 525) ?
525 would be the correct value indeed if the horizontal frequency would be VGA-perfect at 31.4686 kHz -> 31.4686 / 525 = 59.94 Hz refresh rate.
However as I mentioned earlier in the same post:
For my VGA-compatiblity-mode I needed to get the horizontal frequency as close to 31.4686 kHz as possible. My solution was to set register 0 to 63:
16000000 / ((63+1) *8) = 31250 Hz = 31.25 kHz
31.25 kHz is as close as I can get to the original VGA-frequency. And because of that the vertical frequency needs to be a little lower at 521 to get close to 59.94 Hz refresh rate.
Ive been away for a while Miro. I was going to write down some more steps for you to try. However, it looks like I may have damaged my VDC!!
I have tried running my VDC register status program and after a few register changes, the C128D appeared to reset. Thinking it was some sort of bad register setting, I reloaded it and tried again. It got progressively worse, to the point where I was turning the C128D on and it would reset within ~5 seconds. Then once it wouldnt even turn on at all! It acts exactly like I am resetting the computer.
So with this problem, I am pretty much stumped for any further experimentation for now.
However, it has given me some things to think about.
Im thinking that this line of resolution boosting is not particularly practical for most situations. Im not seeing too many people with my exact setup and for those that dont, the lengths I am going to are just not attainable with normal equipment. On going back to my PVM monitor, I couldnt get anywhere close to the same limits and this seems like the case for Miro too. (Not sure what anyone else is getting, as no one has mentioned about trying any of this out). With what has just happened to my setup, I dont blame anyone for not trying too!
It seems that there are 2 options for high horizontal resolution on the 8568:
1.) Pushing the frequency down by extending the total displayed characters. 2.) Increasing the VDC pixel clock.
I have tried the first, to the limits (and it seems to the detriment of both monitor and VDC!) and can only conclude at this present time, that the VDC is a DELICATE piece of silicon!
More updates when I have time to figure out what is wrong.
@ Hydro: dont worry Im not sure why the pictures you are seeing are of poor quality though..?
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After all the amazing work done here, I was wondering if anybody had collected the information on "good" screen modes and the settings used for them? It would be nice to have a single page showing the VDC register settings used, the details of the output given etc. I am working on another VDC project and wanted to take into account as many strange modes as I can If anybody knows the various modes used in the risen demo too it would be helpful.