One thing about vintage computers is that they depend greatly on whether or not one can plug a compatible monitor into them. That’s what’s behind [Tube Time]’s Graphics Gremlin, a modern-design retro ISA video card that uses an FPGA to act just like a vintage MDA or CGA video card on the input end, but provides a VGA port for more modern display output options. (Actually, there is also an RGBI connector and a composite video out, but the VGA is probably the most broadly useful.)
Why bother making a new device to emulate an old ISA video card when actual vintage video cards are still plentiful? Because availability of the old cards isn’t the bottleneck. The trouble is that MDA or CGA monitors just aren’t as easy to come across as they once were, and irreplaceable vintage monitors that do still exist risk getting smashed during shipping. Luckily, VGA monitors (or at least converters that accept VGA input) are far more plentiful.
The reports of the death of the VGA connector are greatly exaggerated. Rumors of the demise of the VGA connector has been going around for a decade now, but VGA has been remarkably resiliant in the face of its impending doom; this post was written on a nine-month old laptop connected to an external monitor through the very familiar thick cable with two blue ends. VGA is a port that can still be found on the back of millions of TVs and monitors that will be shipped this year.
This year is, however, the year that VGA finally dies. After 30 years, after being depreciated by several technologies, and after it became easy to put a VGA output on everything from an eight-pin microcontroller to a Raspberry Pi, VGA has died. It’s not supported by the latest Intel chips, and it’s hard to find a motherboard with the very familiar VGA connector.
The best laid plans of mice and men oft go awry. At least that’s what we’d tell ourselves if we couldn’t find a 30-year-old computer monitor. [Andrew] picked up an old IBM XT on eBay recently and tried to get the video working. He hasn’t seen any success yet, but the way he goes about solving this problem is very clever.
[Andrew] was stuck with a cool old computer with no way to output anything onto a screen. The XT had an MDA port but neither his TV nor his VGA monitor would accept MDA frequencies. As a workaround, [Andrew] connected an Arduino to the XT keyboard port. On the factory floor, IBM workers used the XT keyboard to load code onto the machines while POSTing. He was able to change the frequency of the MDA CRT controller to CGA frequencies, and with the help of some small components got some video working.
The Hsync and Vsync are still off, and [Andrew] hasn’t been able to get the machine to finish POSTing, but he figures he can use the XT keyboard port for bidirectional communication. He’s written a very small kernel to test out a few things, but unfortunately the XT’s power supply died recently. Once [Andrew] replaces that, we’re sure he’ll get his box up and running.