anoop@socrates.ss.uci.edu (Anoop Mangalick) (06/27/91)
I have a question regarding vertical retrace for the DECStation 5000/200PXG and PXG Turbo. We are trying to display images without glitches and with very precise timing. It seems to me that the most straightforward solution would be to determine when vertical retrace is occurring, and write into the frame buffer during that time. Is this possible? If so, then how is this determination made, and how can the frame buffer be accessed directly? Note that we are X/Phigs/PEX novices, and know next to nothing about our hardware except what the technical overview says. I am willing to work to understand the lowest levels necessary to do the job properly, though. Here's something that might shed light on our problem. We have used XCopyArea to copy pixmaps to the window, and that seems to get around the glitch problem, but the images get displayed on the screen at too-long intervals. Does XCopyArea take note of vertical retrace, and if so, why does it seem to operate slower than the refresh rate would allow? Thank you -- anoop@ptolemy.ss.uci.edu