How to enable VGA support?

[OTS]

Hello,
I'd like to enable VGA support on graphics circuits from Intel but fail to do so.

First I set up a display mode using a generation x graphics standard:

• clock generator speed = 152,857,142 Hz
• image refreshing rate = 65 Hz
• x.input drawing area size = 1,920 pixels
• y.input drawing area size = 1,200 lines

So far, this works.

Then I'd like to disable generation x support (if necessary) and enable VGA support:

• # disable output connector
  digital display port B control["digital display port B enable"] = false
• # disable non-VGA plane
  display A plane control["display plane A enable"] = false
• # disable timing control via generation x and enable timing control via VGA
  VGA display plane control["VGA display disable"] = false
  VGA display plane control["VGA centering enable"] = 00|b
• # disable image pipeline
  pipe A configuration["pipe A enable"] = false
  wait until pipe A configuration["pipe state"] == false
• # disable clock generator (digital phase-locked loop)
  DPLL A control["DPLL A VCO enable"] = false
  DPLL A control["DPLL A external clock buffer enable"] = false
• # disable clock generator control via generation x and enable clock generator control via VGA
  DPLL A control["VGA mode disable"] = false
• # enable clock generator
  DPLL A control["DPLL A VCO enable"] = true
  DPLL A control["DPLL A external clock buffer enable"] = true
• # enable image pipeline
  pipe A configuration["pipe A enable"] = true
  wait until pipe A configuration["pipe state"] == true
• # enable output connector
  digital display port B control["digital display port B enable"] = true

Now I would expect, that the clock generator speed changes to one of the VGA clock generator speeds:

• 12,587,500|d Hz (25 MHz / 2)
• 14,161,000|d Hz (28 MHz / 2)
• 25,175,000|d Hz
• 28,322,000|d Hz

But it doesn't. My oscilloscope says, that the speed remains at 153,374,233 Hz.

Does someone know the correct sequence to activate VGA support?

Thank you.

[Hugo_Intel]

Hello OTS

Thank you for posting on the Intel️® communities.  

We will move your question to the correct sub-forum, the team in charge will get back to you soon. 

Best regards,  

Hugo O.  

Intel Customer Support Technician 

[OTS]

I am still interested, if anyone cares.