If you've pressed F2 to enter BIOS Setup (Visual BIOS), it is asking for a resolution of 1024x768, so it isn't an issue of resolution being too high. As for Windows - which controls the resolution of the BIOS Splash (and Windows Startup) screen - the BIOS is required, by spec, to configure for the monitor's highest reported resolution. The only way the "Input Not Supported" message would appear is if the monitor is reporting an unsupported resolution or is not reporting a resolution at all.
Thanks for the quick reply. I'd like to clarify that this device doesn't have an OS installed yet. So, I don't see how Windows OS would get a chance to push for a higher BIOS resolution.
What I observed is that, on a newer monitor, I can see the BIOS splash and also configure it. This monitor reported a resolution of 1600x900 or something. On the other hand, when I plug in this device to my regular monitor (prior to installing any OS), I get the "input not supported" message. This monitor only supports upto 1280x1024.
This is why I conclude that the BIOS is defaulting to a high resolution. Is there a way to make it start with a lower resolution?
The O/S requirement is part of a Microsoft specification, not anything the O/S is telling the BIOS. The specification requires that the BIOS initialize graphics at the default (which is typically the maximum) resolution reported by the monitor (in its EDID data). If the monitor is mis-reporting (or not reporting) its resolution, this would explain what is going on. I have seen some older monitors that misreport, or do not report, their resolution.
No, there is no way to make it start at a lower resolution.