U-Boot, video console, and visual artifacts

[hjalfi]

To me that plaid pattern looks very distinctive as a simple memory fill --- increasing integers written to memory. Although I don't know how this can be appearing on the screen _after_ the text has been drawn, unless it's being orred in, which seems odd. It's possible that the video hardware supports multiple framebuffers, overlayed on top of each other, and u-boot is erroneously enabling the overlay but hasn't told Linux about it.