Mardi Gras full HD


SYS 64738
Feb 8, 2019
Toijala, Finland
We figured out on Discord that this should be feasible. Turns out the Mardi Gras pixel clock limit is 160 MHz, so with this in mind I did come up with the attached VFS. I had to shorten the horizontal front porch by 32 pixels from what was given to me by the modeline calculator to make it work with my monitor. Before trying this I got display regions repeated horizontally, which looked really confusing. You can adjust this as well - I have put comments in the file to show where I've touched the calculated result.

I compiled the vfs file on my Octane with this command line:

vfc -cchip=mgras_vc3.def,board=mgras.def -p '-DRSSCOUNT=1' -p '-DDB32=0' -p '-DINTERLACED=0' -p '-DSTEREO_FMT=0' -p '-DOPTIONS=0' -p '-DZBUF=0' -p '-DVERT_SERRATION=0' 1920x1080.vfs
The options are explained in this excellent wiki article:

This outputs an a.vfo which you can then copy to, say, /usr/gfx/ucode/MGRAS/vof/1920x1080_56.sdb and then use the Display Properties in Toolchest to use that mode. Make sure to note which mode you had before! If the mode does not work or displays incorrectly, log in remotely and copy the earlier mode's file over your custom mode, restart xdm and try again.

Have fun! Also, don't do a web search on mardi gras full hd.


  • Haha
Reactions: Elf


Jul 20, 2019
Glad you enjoyed the wiki article! I spent quite a bit of time updating it after making HD vfo's for my Octane.

I wish there was a good, current, solution for hosting a set of pre-compiled vfos. I have them for 1080p and several other common resolutions.

Edit: more on my experience here:

Edit2: it was so long ago I totally forgot I set up a GitHub page with several customs vfo and sdb files.
Last edited:
  • Like
Reactions: Northsky

About us

  • Silicon Graphics User Group (SGUG) is a community for users, developers, and admirers of Silicon Graphics (SGI) products. We aim to be a friendly hobbyist community for discussing all aspects of SGIs, including use, software development, the IRIX Operating System, and troubleshooting, as well as facilitating hardware exchange.

User Menu