After an eternity of procrastination and wire-wrapping, I finally finished BMOW’s video subsystem. Well, not quite finished really: the character generator is still missing, but the all the hardware is there to support the pure graphics modes. It’s about time!

With anticipation I flipped the power switch and was greeted with: nothing. The monitor turned on, which was promising, but all I saw on the screen was some faint gray noise on a black background. I spent about an hour troubleshooting, trying different video modes and palette settings, with no change. At last I realized a very stupid mistake: I’d forgotten to place all of the discrete components! The current reference, diode, and assorted resistors were still sitting neatly in a box. I put them into their places on the board, turned on power again, I saw this.

I was expecting either blackness, or some kind of static noise pattern, given that the contents of video memory were uninitialized. I wasn’t expecting this, though. Seen live, it’s even stranger than it looks in the photo. The image is flickering and dancing like crazy. It even looks as though the vertical refresh is starting at random locations within the frame, and sometimes it never gets all the way to painting the bottom of the image before it starts again at the top. Ugh. At that point I was tired and discouraged, and went to bed. Hopefully it won’t prove too difficult to resolve.