The SNES is a legendary console, of that there can be absolutely no doubt. However, it did have one considerable weakness when compared to its main rival, the Sega Mega Drive / Genesis: the clock speed of its CPU.
The Ricoh 5A22 which powers the console runs at 3.58 MHz, while Sega's 16-bit system has a Motorola 68000 running at 7.6 MHz (even the 8-bit TurboGrafx-16 / PC Engine has a faster CPU than the SNES, with its custom Hudson Soft HuC6280 CPU running at 7.6 MHz).
The end result of this? Many early SNES title exhibit crippling levels of slowdown because the CPU simply cannot keep up with the on-screen action. Nintendo dealt with this shortcoming by introducing chips which could be included in cartridges to take some of the processing tasks away from the console's CPU, one of which was the SA-1 chip, also known as the "Super Accelerator 1". This chip contains its own processor which runs at 10.74 MHz and boasts other improvements such as faster RAM and memory mapping capabilities.
What in the blazes does this have to do with developments in 2021? Well, remember when we reported back in 2019 that Gradius III, one of the earliest SNES shooters and one utterly plagued by slowdown, had been patched to take advantage of the benefits of SA-1 chip? Well, the man responsible for that hack, Brazilan coder Vitor Vilela, has since released SA-1 patches for Contra III and Super Mario World. Over Christmas, Vilela added another hack to this collection: Super R-Type. He also released a 'FastROM' hack for Super Castlevania IV around the same time, which is the first step towards a full SA-1 update.
All of these games are relatively early releases in the SNES library, primarily because they came too soon in the console's lifespan to benefit from the power of the SA-1 chip (or the Super FX chip, which was even more powerful and would be put to excellent use in games such as Star Fox, Stunt Race FX and Yoshi's Island). All of these games can be played via emulation, but they also work on original hardware, assuming you have access to a compatible flash cartridge.
There are plans to perform the same trick with titles like Axelay and U.N. Squadron. However, this hack can't bring every SNES game back from the brink; Vilela reports that Race Drivin', an early attempt to create 3D visuals on the system, would require a complete coding overhaul to speed things up. This clearly isn't a silver bullet that can fix all of the SNES' slowdown problems.
Developing these patches is a time-consuming process (the Super R-Type hack took over 70 hours to complete) so if you'd like to support Vilela's work, you should consider backing his Patreon. You can download Vilela's currently-available hacks here.