First post, by DamienC
I built an 8-bit ISA Trident TVGA9000 based SVGA card (http://www.malinov.com/Home/sergeys-projects/isa-supervga). I had originally had some issues with unreadable text and posted about it in the General Hardware forum, but after checking over my solder joints the card seemed to be working fine and I deleted that post.
So now, most of the time, the video card works near perfectly in my Micro 8088 based system. It even passed every video test in CheckIt Pro. However, it exhibits some strange behavior:
- Occasionally, on system startup, the system appears to go into some sort of weird "monochrome mode" where text that should be color shows up in black/white/gray, and some normally gray text doesn't appear at all. I can still boot and get to a DOS prompt, but a lot of the text is "hidden," meaning I know something was outputted and saw the cursor move but there's nothing on the screen. When this happens, I can launch a game that uses low res VGA graphics (in this case I fired up Loom), and the game starts up just fine, except with grayscale graphics. Exiting the game brings me back to a visible DOS prompt with gray text, but programs still launch in monochrome mode. This also seems to happen more often when I hit the reset button on the case or with a soft reboot (ctrl-alt-del). It has happened on first boot from power on as well though. It's very inconsistent.
- One game I tried running, an ancient CGA game just called Archery (I have it on an old Software Labs shareware floppy entitled "Arcade Sports Games") does not run at all, system halts on execution. The other two CGA games on the floppy (PC Bowl and PC Pool) work fine.
Anyone have any idea what might be wrong? I've gone over the board a couple times now and all the solder joints seem OK and I didn't miss any ICs.
I'll also try to provide some pictures or video later today to show exactly what this looks like.