The Super Nintendo port of Gradius III is notable for being close to the arcade original, with its large, bright and colorful graphics. However, due to the limitation of the console’s hardware, the port is also well known for having constant slowdowns during gameplay, particularly during later sections. [Vitor] hacked away at the game and made a patched version of the ROM use a co-processor to eliminate those issues.
The slowdown seen here in Gradius is not uncommon to SNES players, many games of that era suffer from it when several sprites appear on the screen at once. This is partially due to the aging CPU Nintendo chose, supposedly in order to maintain NES backwards compatibility before the idea got scrapped. Unable to complete its tasks by the time the next frame needs to be shown, the hardware skips frames to let the processor catch up before it can continue. This is perceived as the aforementioned slowdown.
Around the later stage of the SNES’s life, games started using additional chips inside the cartridges in order to enhance the console’s performance. One of them is the SA1, which is a co-processor with the same core as the main CPU, only with a higher clock rate. By using it, games had more time to run through the logic and graphics manipulation before the next frame. What [Vitor] did was port those parts of Gradius III to the SA1, essentially making it just like any other enhanced cartridge from back in the day.
Unlike previous efforts we’ve seen to overclock the SNES by giving it a longer blanking time, this method works perfectly on real unmodified hardware. You can see the results of his efforts after the break, particularly around stage 2 where several bubbles fill the screen on the second video.
[Via Ars Technica, thanks Damian for the tip!]