| QUOTE (Foe-hammer @ Apr 30 2004, 06:42 PM) |
Higher resolutions are possible with the two vga bios. The problem you are having is your cable. You have to have an HD cable, or set the right pin settings for HD, to access 720p and 1080i in the ms dashboard. If you set pin 11 to 9, the cable will go into vga mode (GOG), and only 480p will be possible; 720p and 1080i will not even show up as an option in the ms dash. I am using a modified HD cable, and I get 720p and 1080i with the vga bios.
The only problem with the higher res settings is there is a color ratio imbalance; too much red and not enough blue in the picture. Making playing games in 720p or 1080i useless. Some monitors will display the color ratios correctly, but a lot of monitors don't work correctly in 720p and 1080i due to the syncs used in the higher modes. Basically in 480p the sync pulse in the video is "bi-level" meaning it only goes negative and the vga bios is designed to "clip" that negative sync off. 720p and 1080i use a "tri-level" sync meaning the sync goes negative and then positive. The vga bios are only able to clip the negative portion off but can not do anything about the positive portion of the video. A lot monitors will interpret this positive sync tip as color info and sample the black reference level incorrectly. I expect there may be a way to fix that with the VGA BIOS if it is designed to switch the video encoder to use "bi-level" syncs for those video modes.
The other main problem, as you have stated, is a lot of good xbox games, including the n64 emu's, turn green after the initial boot. |
Question: is this based on using either a SoG capable monitor or with an LM1881-based circuit?
Over at Xbox-Linux, Oliver suggested tapping the internal H/V signals running between the xGPU and video encoder chip. He also included pics of the points needed to tap said signals, though I could only verify them for the v1.0 board (I don't have a v1.1 board to check those points). His idea with this is that it'll alleviate the color problem since you would have pure sync singals instead of "separating" a composite sync singal from the green signal (or letting the monitor do that with a SoG capable monitor).
I was planning on doing this mod, but another mod I was working on killed my v1.0 board. Once I get a new board, and this mod up and running, I'll be posting my results in the Xbox Audio/Video area of the forums (which will go with spillage's homemade case and a shitload of audio and video outs to go with it).
And to answer the question before it's asked here...yes, you'd still need a VGA debug BIOS even with tapping the board for pure sync signals. This was asked in the Audio/Video part of the forums and I thought I should keep that clear.
