why did bart allen absorb the entire speedforce and how fast is he and how fast is superboy prime

Bart Allen, also known as Impulse and later as the Flash, absorbed the Speed Force during the storyline "The Flash: The Fastest Man Alive." This event occurs when Bart is faced with an overwhelming threat and needs to tap into the Speed Force to save the day. The Speed Force is a mystical energy field that gives speedsters their incredible abilities, and absorbing it allows Bart to gain immense speed and power. As for his speed, after absorbing the Speed Force, Bart's velocity would be significantly enhanced, making him one of the fastest characters in the DC Universe. While there isn't a specific speed limit established after he absorbed the Speed Force, speedsters often operate on a different scale, including the ability to outrun light or even time itself. Superboy Prime, on the other hand, is a character from the "Crisis on Infinite Earths" storyline and is an incredibly powerful foe. His speed is often portrayed as immense, potentially rivaling or exceeding that of the Flash. After various power boosts throughout the storyline, Superboy Prime can reach speeds close to light speed, if not beyond. Both characters exist in a universe where the concept of speed can be somewhat fluid and often compared in terms of feats rather than fixed numbers, so direct comparisons can be tricky. However, they are both considered among the top speedsters in the DC Universe.