When I was tidying up my garage I found an old 386SX laptop with an 8" passive LCD screen. After thinking really really hard and failing to find a use for it, I decided that I'll take it apart and then hook up the passive LCD screen to my linux box and have it sit there scrolling web server logs. Would that not be impressive? I think so. A reasonably complex idea, especially keeping in mind that I would have to rewire the 15-pin VGA plug and hook that up to the LCD inputs.

Then I started to think further, and did some research on the topic. What I found out didn't exactly impress me.

Generally, it is considered impossible to connect an LCD screen to a VGA card's output. The way that LCD screens work is that they have graphics controller chips (a Cirrus Logic one in my case) that have two output ports:
  • One for external analog VGA output.
  • The other for digital control of the LCD.
Graphic LCDs are notoriously non-standard and, even to the extent that they are becoming more standard, were horribly non-standard during the time at which most 386 and 486 laptops were made. So the main problem here is that VGA cards have an analog output, and the LCD screens have a digital input.

With my no-brand LCD panel and a random LCD controller device that I wanted to talk to the VGA card, I was in for a few days worth of staring at a logic analyzer and hacking driver code. Problem made even more difficult by the fact that I don't even own a logic analyzer.

As I said above, it is generally considered an impossible task. With enough motivation and money everything can be accomplished, and this is no exception. To connect a digital LCD screen to an analog VGA interface you'll need a mixed-signal microcontroller communicating with the panel to translate the analog VGA inputs into the digital signals used in the LCD. There's some pretty complex circuitry involved in this. The commercially available 15-18" LCD panels with SVGA inputs do exactly that, but again, they are expensive and mostly feature proprietary designs. And don't forget that you will also need to write a driver for the newly created hardware.
So basically I gave up on that idea. If anyone knows a reasonably simple way or doing this conversion, please post it. Otherwise, "Top Ten Things To Do With An Old Laptop" would be a node that I will soon have to visit.