first off thanks for taking the time to respond
yes you are right about the interlace, but i also tried it with a "cvt 640 480 60 i" command, and that does creates the 640 by 480 interlace mode, but that did not work either.
I am only using my machine for mame with groovymame, not for consoles
I believe you might be right about the fixing games not filling the whole screen that the EDID will not be the solution
There must be a way however somehow to tell groovymame or switchres what the screen dimensions are and about that i found this webpage that discussed modelines and quoting here only the piece at the bottom of this page
All modes in this document can be slightly readjusted in order to fit them to particular devices. Each mode follows this general format:
Modeline "Description" FF.FFF HHH HHI HHF HHT VVV VVI VVF VVT (options)
The following simple modifications can be done without redoing the entire mode.
Position shift: to shift the picture left or right add or substract the number of pixels you want to shift to the HHI and HHF values equally. Keep in mind the limits: HHI cannot be less or equal than HHH and HHF cannot be greater or equal than HHT.
The same procedure is used for vertical shifting with values VVI and VVF.
Size/resolution reduction to reduce picture size lower HHH or VVV. This will cut the picture from its right or bottom side respectively, leaving black bars and keeping pixel aspect. Once done, you will have to select the new resolution and may have to center the picture again (position shift).
Picture width: it is possible to adjust picture width keeping the same resolution by adjusting pixel aspect. Modify HHT, a lower value means wider pixels. Then FF.FFF has to be recalculated multiplying HHT by the desired horizontal frequency in MHz, that is 0.015625 for PAL, 0.015734 for NTSC or 0.02496 for 25kHz arcade screens). HHT cannot be less or equal than HHF and FF.FFF must not exceed the maximum pixel clock allowed by the video card.
Horizontal resolution doubling: some old video cards like Matrox do not support the low resolutions used in most old videogames. To correct this problem multiply by two these values: FF.FFF, HHH, HHI, HHF, HHT and set the emulator to use the new resolution.
This sugests that there is room to adjust the modelines by tweaking the values, but i do not have a clue where groovymame stores these and if they could be adjusted this way, if that solves it, i would be willing to work on adapting them to my screen needs if that's what it takes to get the games correctly centered and fullscreen
This adjusting modeline smells like it will be time consuming but i would be willing to give a crack at it if that solves my problem.