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MXM 2.1 software & hardware specification leaked!

.NetRolller 3D

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The MXM 2.1A specification (including a full description of the MXM structure) has leaked on a site called borec.cz

The software specification can be found @ www.mxm.borec.cz/software_spec.pdf, while the electro-mechanical spec is @ www.mxm.borec.cz/Electro_mech_spec.pdf

The software spec includes a description of the MXM structure, plus the interfaces required for reading it - this may be of interest to BIOS modders working on fixing the 30-second beep problem ("MXM structure not found or invalid").

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Guest quipster

Yes, but only a workaround on the card side. With this information, it is possible to interpret & reconstruct MXM structures found in system BIOSes, allowing potential MXM structure errors to be fixed.

Another problem that can be fixed this way is the lack of POST display when a 9600M GT is installed in an Acer 6920G or 8920G. The output device structure for the HDMI port of the 6/8920G is 0x00F9F78A2120, which parses to:

Device type: TMDS (DVI or HDMI)

DDC port: DDC-B (MXM pins 230 & 232)

Connector: HDMI Type A socket

Connector location: External

Link type: Single-link DVI/HDMI connected to TMDS link A

HDMI SPDIF audio source: No audio

Digital signal drive strength: Normal

Digital reserved field 1 (2 bits, should always be 11): 01 (incorrect, violates the MXM spec!)

Output select GPIO: None

DDC select GPIO: None

Device detection GPIO: #0, active low (logic low on GPIO pin 0 indicates a display plugged into the HDMI port)

System hot plug notification: Disabled

I suspect that the culprit is Device detection GPIO, which is presumably always low/0 on this machine, indicating a device plugged in! Because the boot display order is VGA first, then HDMI, finally internal display; connecting a display to HDMI (or fooling the MXM VGA into thinking one is connected) suppresses POST display on the internal LCD, and directs it to the HDMI port. When Windows finally boots up, it recognizes the internal display and makes it primary (Windows always considers the internal display primary by default, regardless of the MXM structure), so display in Windows is normal.

I therefore think that hexediting the HDMI port's output device structure to 0x3EF9FF8A2120 (changing device detection GPIO to None) should solve this issue.

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