Resurrecting an XT

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.

Gaming on an IBM XT using an NES controller

[Frode] felt that using the keyboard for gaming on his old IBM XT computer was simply too noisy. He came up with a much quieter way to game by building an XT adapter for an original NES controller. If you haven’t explored the communication protocol used by the NES peripherals this is a great way to learn. Inside you’ll find a CMOS shift register that captures button states when it receives a latch signal. With that in mind [Frode] came up with a circuit to gather the bits from the controller, and generate input commands using the XT keyboard protocol without using a microcontroller. All of this is explained in the demo after the break.

Most of the NES controller hacks we see permanently alter the hardware. It’s nice to see one used without cracking it open.

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XT IDE controller

[Geordy] wanted to use some IDE devices but he didn’t have an interface card for his XT system, which can’t handle 16-bit  IDE. He looked around for 8-bit ISA controllers but they were hard to find and quite expensive. Lucky for him there’s an open source project that makes a solution to this problem. The XTIDE project brought together a group of vintage computing enthusiasts to design this ISA card. [Geordy] was even able to order a professional PCB from one of the forum members. He ordered the parts an soldered it together, costing about $30 total. He had a friend help him burn the code to the EEPROM but that’s easy enough to do with an Arduino, Bus Pirate, or one of several other methods. Now his grand plans at installing DOS 6.22 have been realized.

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