One of the remarkable characteristics of the Super Nintendo was the ability for game cartridges to pack more than instructions and assets into ROM chips. Super Mario RPG PCB. Above, a Mario RPG PCB. Notice the absence of CIC chip, a ROM chip in U1 containing the game instructions and assets, a SRAM chip in U2, and the SA-1 in U3. Notice there is no oscillator since the SA-1 uses the System Master clock line from the cart port and halves it internally. The SA-1 CPU and the Super NES CPU operate simultaneously, which results in five times greater performance of the Super Accelerator System over the current Super NES. - Super Nintendo Developer Manual Book II. Thanks to the improved processing, the SNES is able to animate and detect collisions on all 128 sprites available in the PPU. The horsepower also allowed to transform sprites on the fly and write them back into the PPU VRAM. The dramatic improvements were demonstrated in a Nintendo SA-1 demo cart.

Source: Inside the Super Nintendo cartridges