Software Support > GroovyMAME
Trying to create monitor presets for KT-2914 (Betson-Kortek) MultiSync
Calamity:
Hi RetroACTIVE, sorry I'm too busy lately.
I saw your results. I'll try to explain what I think it's happening.
Your monitor seems to apply different settings depending if vfreq is lower or higher than 60 Hz. If it's below 60 Hz, normal settings produce huge overscan. If it's above 60 Hz, the results are quite reasonable. The important thing to understand is that the behavour is not linear, there's a point nearby 60 Hz were the monitor decides to jump to either one of the modes. The way to solve this will involve creating two separate monitor_specs lines to deal with each case, so we can compesate for the overscan in modes below 60 Hz by using bigger horizontal porches, etc. But we already knew that.
Fortunately, from your last test we can guess that the trigger vfreq value is somewhere between 59.941 and 59.981 Hz.
When you entered the toki values, you had a huge overscan. Then you increased horizontal porches (well done). But as the vfreq was locked, Arcade_OSD updated the dotclock in order to keep a frequency as close as the original as possible. Being this a low resolution (worse precision) and due to dotclock granularity, the closest resulting vfreq happens to be 59.981 Hz.
However, this new vfreq seems to have triggered the 60 Hz adjustments. We know this because the resulting borders are HUGE. You just increased the porches by two characters and the results are not proportional to what you did. The good thing is that now we have a good guess of where the limit is.
Now, you'll need to redo all the steps, right to the state shown on your third pic. Once you're there (59.981 Hz), unlock vfreq and start decreasing the dotclock step by step, so vfreq gets equal or below 59.941. Let me know if you find the sudden jump I'm talking about.
Check the horizontal overscan. If you need to readjust, repeat the process (lock vfreq -> increase horizontal porches -> check if we're under 59.941 otherwise unlock vfreq -> decrease dotclock, etc.) until you get a good adjustment for games under 60 Hz.
RetroACTIVE:
Allrighty... we'll see if I got this corect...
I have to go back and double check what I did...but here it is.
--- Quote ---Now, you'll need to redo all the steps, right to the state shown on your third pic. Once you're there (59.981 Hz), unlock vfreq and start decreasing the dotclock step by step, so vfreq gets equal or below 59.941. Let me know if you find the sudden jump I'm talking about.
--- End quote ---
Decreasing the vfreq didn't cause it to jump to another mode... It just immediately produced the over scan.
I went back and forth with locking vfreq and adjusting porch values and was able to get this geometry worked out pretty darn good...
Hopefully I didn't miss a critical step here.
Calamity:
--- Quote ---Decreasing the vfreq didn't cause it to jump to another mode... It just immediately produced the over scan.
--- End quote ---
Yes, that's the jump that I meant: a sudden jump in geometry not proportional to our settings. There it is.
So, these settings in your last pic are the ones we need for resolutions below 60 Hz. Now, they're still not quite right because the hsync pulse is artificially big, it should be around 4.7 microseconds. It just works fine because HFP + HSP + HBP total time is the right one, but I'd try to redistribute the individual values to something like HFP = 7, HSP = 4, HBP = 7.
RetroACTIVE:
Hey Cal,
I went back to try and tweak the values... its really not cooperating below 59.981Hz while I'm trying to keep the sync pulse around 4.7us
This is the closest I could get without the monitor popping into some other mode:
I need to go back and check, but generally to get it to go below 59.941Hz the best I can do is get it adjusted to the settings you see above, otherwise the image pops it into the center of the screen and the margins are really large. Then when I try to adjust the porch values, it pops back out beyond the edges.
I'll post more photos to show you what is going on.
Calamity:
That's a perfect fit so I'd use those values. You won't get a 4.7 value for h sync pulse because you're working with a very low resolution, that's normal.
--- Quote from: RetroACTIVE on March 13, 2012, 11:08:46 am ---I need to go back and check, but generally to get it to go below 59.941Hz the best I can do is get it adjusted to the settings you see above, otherwise the image pops it into the center of the screen and the margins are really large. Then when I try to adjust the porch values, it pops back out beyond the edges.
--- End quote ---
Interesting. However, can you double check if adjusting the exact same settings you have above, but just changing the horizontal values to 7, 4, 7, makes the image pop into the center of the screen?? I'm working on the assumption that what triggers the mode change is the vfreq value, but the settings I'm suggesting should leave the vfreq alone, it's just that the picture would be a bit shifted to the left.