How do the FFB2/2+ and the PGX determine their default resolutions?
Until recently, all frame buffers read a “sense code” from the 13W3 connector or adaptor to determine what resolution the monitor supported. This mechanism has now been superceded by a system called DDC (Display Data Channel). DDC is a Vesa standard which allows the frame buffer to read information known as EDID (Extended Display Identification Data) from the monitor. This information includes resolutions supported, max width, max refresh, sync type and so forth. After reading the EDID upon bootup, the firmware looks at the EDID Standard Timing Identifiers. It compares each value against the list of supported resolutions. If there is a match, that resolution is set and the resolution selection process is complete. If not, this process continues until all of the Standard Timing Identifiers have been tested. At this point a resolution of 1152x900x66 is chosen. The first Sun monitor to support DDC was the Sony “N2” or GDM 20E20.
