DVI VSA-100 image offset

    I first noticed this on the Voodoo4 M4800, when using DVI, the image is shifted to the right by about 4 pixels. The unused pixels can be clearly seen in this photo:


    Did some testing, and the same happens when using a DVI Voodoo5 5500 in a regular PC. I tried with SFFT1.9 and amigamerlin 3.1 R1 under XP SP3, no difference.


    Using Intel Graphics:



    Using the Voodoo5:



    This happens regardless of the resolution, on all the HDMI monitors I used for testing.


    While I can fix this from the FPGA on the Voodoo4 M4800, if this is an issue affecting all DVI VSA cards, it would be nice to find an universal fix.


    If anyone can test this, I would highly appreciate it. Testing method is simple, connect a V4/V5 DVI to a monitor, look closely at the left side of the panel. Then connect any Nvidia/AMD/Intel/whatever HDMI card to the same monitor, and look closely at the left side.


    If you're doing this, regardless if it has the offset or not, please provide details of the card used, driver version, video bios revision and OS.

    Yes, this happens at any resolution, even 4:3 on 16:9 displays (can be seen depending on the contrast/brightness settings of the panel).

    I can dump EDIDs, but this happens with all the HDMI displays I used for testing, all different models.

    And the Voodoo4 M4800 has an EEPROM with an EDID generated by me, and it behaves the same.

    We could try to change the EDIDs, i.e. Reduce the horizontal back porch by four pixels and check if this helps. Front porch must be then increased if I am not wrong.

    VSA cards don't seem to do that much with the EDID. For DVI, it needs to be there on power on, to have the card switch to it (otherwise only VGA will work, although this can be patched in the VSA BIOS), and maybe to correctly display the boot screen.

    In Windows, it doesn't seem to care at all about EDID. Timings used are the ones in the system registry, example:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\3dfxvs\Device0\TIMINGS\1920,1080\60Hz


    I have tried messing with those as well, tweaking the horizontal back/front porch in both directions, it doesn't do anything.

    On the Voodoo4 M4800, I'm not using a SIL164, it was replaced by an FPGA.

    On regular V4 and V5 DVI cards, if I'm not mistaken, the SIL164 is configured via hardware straps and the I2C interface isn't used.


    Edit:

    On regular V4/5 cards, the SIL164 is configured correctly. The image would be messed up with it was latching on the wrong edge. Also, it wouldn't shift the whole image by 4 pixels.

    Edited once, last by sdz (August 16, 2024 at 10:04 PM).

    • New

    I have an update on this. While under XP, with V4 and V5 cards, SSFT and amigamerlin drivers, the issue happens, there is no offset under Windows98 with the official 3dfx drivers.