Hi Carmona,
Thank you for your reply!
I have thought about cable issues, but as my MacBook Pros works with the same cables I have ruled that out.
I have used the VBIOS for Baytrail on several manufacturers boards and products and it always worked. I have my own BIOS, which has all the standard APIs of the legacy BIOS, some unique internal APIs, no setup and are customised to the product. The BT BIOS has been used on several products due to its speed and functionality.
Many products are still based on Baytrail architecture, so I adopted the BIOS to two mini PCs with J1900 and dual lan yesterday. It worked immediately both for VGA and HDMI port, with HDMI as the primary port. The VBIOS was configured with the BMP tool.
As products based on Braswell/Cherryview is still available, I adopted the BIOS to a N3050-based CRB. However, here the VBIOS doesn't work at all. With the security settings from BWG I get a blanked screen without a cursor in the resolution 1920x1080. So the resolution is right as the image will be scaled up by the hardware to the monitors preferred resolution.
When adding the DRM trusted security setting, I get the cursor at the right location with the same resolution as above. However, everything is blinking in the same phase as the cursor and instead of the BIOS title message I see only colourful rectangles. As the BIOS title message is one row in 25x80 mode and two rows in 25x40 mode, followed by two line feeds, I can confirm that the VGA cursor is operating correctly for VGA mode on HDMI.
Intel made several changes in the BW/CHV architecture and several VBIOS versions spanning from 1002-1014. They also added write protection to VGA registers, so in order to program these registers you need to either enable VGA in the VGA control register or you needed to call a special routine to lock up the VGA register. This routine used some IBM CGA registers to lock up the VGA register in question with an algorithm based on the value of the target register.
Intel dropped the VGA support after that, so it's unknown wether VGA on HDMI or DP has ever worked on BT/CHV architecture. Perhaps they messed up and that's the main reason why VBIOS was dropped. In previous architectures there was a VGA port, so some of the electronics might be part of the engine driving the VGA mode.
I know some vendors has used the SDVO to get the VGA port support by an external chip. Nevertheless, it's not clear wether the VGA video modes can work on the ePD, DP or HDMI ports. So I need to know if it's an hopeless mission due to hardware malfunction or it can be done by programming some undocumented registers and bits.
The reason for my concern is that Z8350 would be the perfect choice for a big volume product I'm working on at the moment. It's cheaper, smaller and more power efficient than E3845. I know it's EOL, but I think with big enough volumes Intel can be persuaded to produce the chip.
I need to decide if I have to give up my BIOS project with BW/CHV architecture. I think someone at Intel will know if VBIOS has ever worked with VGA video modes. As you don't have support for the architecture, it will not be too much to ask for confirmation about the VBIOS compliance with VGA video modes.
Best regards,
B-O
