Final answer:
A disk buffer is used to mitigate the speed differences between a computer's RAM and the hard drive, serving as temporary storage.
Step-by-step explanation:
The memory buffer used to accommodate a speed differential is called a disk buffer. A disk buffer (also known as a cache), is often found in hard drives and serves as a temporary storage area where data is held while it is waiting to be transferred or while the data is being processed. This helps to balance the speed difference between the high-speed operation of a computer's RAM and the slower speed of the hard drive.
Other options such as a stack pointer, an accumulator, or a CPU cache (not to be confused with a disk buffer) serve different functions. A stack pointer helps to keep track of the position in the memory's call stack, an accumulator is a register in the CPU that accumulates results of arithmetic and logic operations, and a CPU cache is a small, fast memory location close to the CPU designed to speed up the access to data and instructions by storing recently used or frequently accessed data.