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965 with ADD2 card - support for DDC on DVI outputs?

We are developing a Linux application for display monitor control using DDC/CI. We have managed to support most Intel chipsets with DSUB15 analog video using "I2C bit banging" on the DDC_CLK/DDC_DATA (DDCA_CLK/DDCA_DATA) lines using memory mapped PCI bus access with the GPIOA I/O Control register.

However now we are trying to support a G965 system with a dual DVI ADD2 card. From the documentation we can find, there are two pairs of I2C lines (MDDC_CLK/MCCD_DATA for DVI port 2 and MDVI_CLK/MDVI_DATA for DVI port1). These look like they are what we need to access the I2C lines on the DVI ports.

Are these lines memory mapped like the VGA/DSUB15 lines are using a GPIO port? i.e. is it possible to use "bit banging" with them also, or is it necessary to use the I2C controller to access them?

Out of interest, is there a register/memory map of the G965 available?
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I am aswell working on similar issue, and unable to achieve DDC on DVO ports.

could you get any help for your query ? and can you please share is you have received any help in this issue.


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I think we have the same problem. On a 855GM I can access registers 0x5010 VGA port and 0x501C-DVI port. But on Q965 EDID and DDC/CI is only available on 0x5010?

Hope you could share your solution.

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The Intel Open Source Technology Center graphics team is pleased to announce
the immediate availability of free software drivers for the Intel 965
Express Chipset family graphics controller. These drivers include support
for 2D and 3D graphics features for the newest generation Intel graphics
architecture. The project Web site is

This release represents the start of a long term effort by Intel to work
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still in need of significant testing, tuning and bug fixing before
they'll be ready for production use. We're releasing them now to
demonstrate our ongoing commitment to providing free software drivers
for Intel hardware.


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