Intel GMA 900 (915G) - interlaced modes?

Krzysztof Halasa khc at
Wed Jan 3 17:00:44 PST 2007

Keith Packard <keithp at> writes:

> Yes, but as you've deduced, there isn't any software support, not even
> in the modesetting branch (which you'll have to use in this case). 


> The register definitions in the header files should be sufficient to
> enable this, but frankly, I'd buy a different monitor :-)


I just want to move from old EPIA-M which has problems with TV field
parity and can't do VGA->SCART RGB due to lack of interlaced modes.
I'm thinking about buying something cheap like MSI Hetis with GMA900
but it would have to do interlaced modes (I assume with 2x pixel
clock, something like PAL 1440x576i with hardware scaling from
720x576 YUV etc).

I know there are specialized TV (S-VIDEO) encoders but SCART RGB
would be much better in terms of quality (tested with Radeon+RGB
vs. EPIA with "noscale") and stability.

Back to the headers...

grep -ir interlace .|grep h shows something like:


Is that it? I believe VGA output should be connected to analog
port, does that apply to it? I'm under an impression that the
above has something to do with I^2C and external parts.

./i810_reg.h:#define INTERLACE_CNTL       0x70 /* p264 */
./i810_reg.h:#define INTERLACE_ENABLE         0x80 
./i810_reg.h:#define INTERLACE_DISABLE        0x00 

That would be nice but it's only for older chips, isn't it?

Perhaps I'm missing something?

Of course I can try to set 1024x768 32 bpp 87Hz(I) mode with BIOS
and look for register values but will the BIOS let me set it?
Krzysztof Halasa

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