The Mystery of the Missing Pixels

One goal when I started my GPGPU project was to be able to display 3D graphics with my FPGA board on a VGA monitor. This required me to add an SDRAM controller, since there is not enough block SRAM on the FPGA to contain an entire VGA framebuffer. I managed to execute code running out of SDRAM on the processor, and display static images on the monitor. But, to my dismay, when I tried to render animations in real time, the monitor displayed garbage. I imagined all kinds of gnarly data corruption bugs that could exist in the SDRAM controller. Stepping through millions of memory transactions to find the problem was enough to make me want to go back to writing software.