CPU cache
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A CPU cache is a hardware cache used by the central processing unit (CPU) of a computer to reduce the average cost to access data from the main memory. A cache is a smaller, faster memory, located closer to a processor core, which stores copies of the data from frequently used main memory locations. Most CPUs have a hierarchy of multiple cache levels, with different instruction-specific and data-specific caches at level 1. The cache memory is typically implemented with static random-access memory (SRAM), in modern CPUs by far the largest part of them by chip area, but SRAM is not always used for all levels, or even any level, sometimes some latter or all levels are implemented with eDRAM.
Motherboard of a NeXTcube computer (1990). At the lower edge of the image left from the middle, there is the CPU Motorola 68040 operated at 25 MHz with two separate level 1 caches of 4 KiB each on the chip, one for the instructions and one for data. The board has no external L2 cache.
Example of a motherboard with an i386 microprocessor (33 MHz), 64 KiB cache (25 ns; 8 chips in the bottom left corner), 2 MiB DRAM (70 ns; 8 SIMMs to the right of the cache), and a cache controller (Austek A38202; to the right of the processor)