Comment 9 for bug 992346

I ran the xedid script but it did not allow me to use the monitor in question. (I have an irun ZT-SH270QHD.)

get-edid says:
get-edid: get-edid version 2.0.0

 Performing real mode VBE call
 Interrupt 0x10 ax=0x4f00 bx=0x0 cx=0x0
 Function supported
 Call successful

 VBE version 300
 VBE string at 0x11100 "NVIDIA"

VBE/DDC service about to be called
 Report DDC capabilities

 Performing real mode VBE call
 Interrupt 0x10 ax=0x4f15 bx=0x0 cx=0x0
 Function supported
 Call successful

 Monitor and video card combination does not support DDC1 transfers
 Monitor and video card combination supports DDC2 transfers
 0 seconds per 128 byte EDID block transfer
 Screen is not blanked during DDC transfer

Reading next EDID block

VBE/DDC service about to be called
 Read EDID

 Performing real mode VBE call
 Interrupt 0x10 ax=0x4f15 bx=0x1 cx=0x0
 Function supported
 Call failed

The EDID data should not be trusted as the VBE call failed
EDID claims 255 more blocks left
EDID blocks left is wrong.
Your EDID is probably invalid.

/var/log/Xorg.0.log says:
  552 [ 28.729] (WW) NVIDIA(GPU-0): The EDID read for display device DFP-0 is invalid: the
  553 [ 28.729] (WW) NVIDIA(GPU-0): checksum for EDID version 1 extension is invalid.
  554 [ 28.729] (--) NVIDIA(GPU-0):
  555 [ 28.729] (--) NVIDIA(GPU-0): Raw EDID bytes:
  556 [ 28.729] (--) NVIDIA(GPU-0):
  557 [ 28.729] (--) NVIDIA(GPU-0): 00 ff ff ff ff ff ff 00 04 68 fa 00 00 00 00 00
  558 [ 28.729] (--) NVIDIA(GPU-0): 28 15 01 03 a5 3c 22 78 22 6f b1 a7 55 4c 9e 25
  559 [ 28.729] (--) NVIDIA(GPU-0): 0c 50 54 00 00 00 01 01 01 01 01 01 01 01 01 01
  560 [ 28.729] (--) NVIDIA(GPU-0): 01 01 01 01 01 01 56 5e 00 a0 a0 a0 29 50 30 20
  561 [ 28.729] (--) NVIDIA(GPU-0): 35 00 55 50 21 00 00 1a 00 00 00 fc 00 51 48 44
  562 [ 28.729] (--) NVIDIA(GPU-0): 32 37 30 0a 20 20 20 20 20 20 00 00 00 fc 00 51
  563 [ 28.729] (--) NVIDIA(GPU-0): 48 44 32 37 30 0a 20 20 20 20 20 20 00 00 00 fc
  564 [ 28.729] (--) NVIDIA(GPU-0): 00 51 48 44 32 37 30 0a 20 20 20 20 20 20 01 b0
  565 [ 28.729] (--) NVIDIA(GPU-0):
  566 [ 28.729] (--) NVIDIA(GPU-0): ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
  567 [ 28.729] (--) NVIDIA(GPU-0): ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
  568 [ 28.729] (--) NVIDIA(GPU-0): ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
  569 [ 28.729] (--) NVIDIA(GPU-0): ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
  570 [ 28.729] (--) NVIDIA(GPU-0): ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
  571 [ 28.729] (--) NVIDIA(GPU-0): ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
  572 [ 28.729] (--) NVIDIA(GPU-0): ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
  573 [ 28.729] (--) NVIDIA(GPU-0): ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
  574 [ 28.729] (--) NVIDIA(GPU-0):
  575 [ 28.729] (--) NVIDIA(GPU-0): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  576 [ 28.729] (--) NVIDIA(GPU-0): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  577 [ 28.729] (--) NVIDIA(GPU-0): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  578 [ 28.729] (--) NVIDIA(GPU-0): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  579 [ 28.729] (--) NVIDIA(GPU-0): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  580 [ 28.729] (--) NVIDIA(GPU-0): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  581 [ 28.729] (--) NVIDIA(GPU-0): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Running xedid as root produces no output and exits with code 0. Rebooting after running the script has no effect.

$ uname -a
Linux lovecraft 3.5.0-17-generic #28-Ubuntu SMP Tue Oct 9 19:31:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

This is on Linux Mint 14; I'll retest with an ubuntu livecd at my earliest convenience.