HARD CORE

Last Christmas, José Tejada encountered a weird issue in Contra. A player of his recreation of Konami’s original arcade PCB had reported that the music was playing too slowly if you compared it with the genuine 1987 hardware. The pitch was right, but the pacing wasn’t – and that, to Tejada, was very odd.

You’d be hard-pressed to find someone in the world with a better understanding of Contra’s PCB and its Yamaha YM2151 sound chip than Tejada, known as Jotego in retrogaming circles. A microelectronics engineer with a love of classic videogames, he’d become interested in reverseengineering the chips that defined the sound of many arcade games, computers such as the MSX range, and consoles such as Sega’s Mega Drive, so that he could simulate them perfectly on his PC. He’d painstakingly measured the voltages and timings of the original chips, figuring out exactly how they directed flows of data around them. To find his recreation not performing exactly as it should, then, was a surprise.

So Jotego dug once again into the minute architectures of Contra’s PCB and the YM2151, following connections between components until he found an anomaly in the way the real Yamaha uses the PCB’s power-distribution unit as a timer for its music. Jotego’s recreation had made a logical assumption about how the chip’s timer operates, and it didn’t match: the Yamaha timer was failing to properly reset itself as it looped. “So the Yamaha design was actually wrong, because the counter was out of control!” Jotego says. This tiny error, made decades ago when the chip was designed, was inserting random values into the timer which has meant that, ever since its release in 1987, Contra’s music has been running just a little faster than it was meant to.

This detail is the tiniest of footnotes in the annals of gaming history, but it shows the level of precision that modern recreations of old games, like those of Jotego, can reach. Or more specifically, recreations of old games running on MiSTer, an opensource retrogaming system using a programmable chip called an FPGA to recreate hundreds of different arcade PCBs, consoles, ZX Spectrum, , PC Engine, a 486 PC, Neo Geo, Super Nintendo, ; the list swells with each passing month, as its community of programmers and engineers makes new ’cores’ – sets of configurations for MiSTer’s FPGA which make it behave just like original hardware.