The first new Model 3 program in 17 years?

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The first new Model 3 program in 17 years?

Postby Bart » Sat Dec 26, 2015 9:49 pm

I spent the past week at my parents' place and decided to tackle a project that I've wanted to do for years: run my own code on a Model 3 PCB. I've had a VF3 PCB lying around here for a good 10-12 years. The previous owner put it in a nice case with fans and even included an ATX PSU wired up to be used with it. Originally, I was unable to obtain a monitor compatible with the Model 3's medium frequency timing, and so it collected dust until last year, when I discovered that an Acer LCD monitor my parents had worked great with it.

A few weeks before coming out here, I built a Windows-hosted powerpc-603e-eabi cross compiler (gcc 5.1.0) and set about writing a simple test program and all the required startup code. I added support to Supermodel for loading arbitrary ROM images and, with the aid of the excellent debugger Nik wrote, managed to write a simple program that could print text to the screen using the tile generator. Getting that far was more work than I expected! I then went on an eBay shopping spree and purchased a cheap device programmer (which I am very pleased with), EPROM eraser, IC extraction tool, a few sets of M27C4002 EPROMs, and an assortment of components I thought I might need.

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Dumping my VF3 EPROMs using the MiniPro!
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Backstage at Supermodel HQ.
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With everything seemingly ready to test out my super-simple "hello, world" program, I carefully connected my VF3 board to its power supply, removed the four VF3 EPROMs, inserted my replacements, held my breath as I flipped the power strip switch on and ... nothing! A black screen! How was I going to debug this? There is quite a lot of setup involved in bringing up a PowerPC system that Supermodel cannot emulate (such as the MMU), so the problem could have been anywhere. Fortunately, I was able to flash patterns on the board LEDs to determine that my code was indeed running. The problem lay with the tile generator. Now it so happens that Model 3 uses the System 24 tile generator, so I fired off an email to Charles MacDonald who pointed out a few things to me. I began debugging by using Supermodel to capture everything Virtua Fighter 3 writes to the tile generator and system registers up until the region warning screen shows up, creating a sort of "save state" I could test on the actual hardware. Th