Does onchip cache in microprocessors use SRAM DRAM or Flash

Does on-chip cache in microprocessors use SRAM, DRAM, or Flash? Why???

Solution

cache is used to reduce the average time to access data from the main memory. The cache is a smaller, faster memory which stores copies of the data from frequently used main memory locations.

In x86 microprocessor, DRAM used for main memory had significant latency, up to 120 ns, as well as refresh cycles. The cache was constructed from more expensive, but significantly faster, SRAM memory cells, which at the time had latencies around 10 ns. SRAM is expensive but faster than DRAM.

Current research for Cache memory

Early cache designs focused entirely on the direct cost of cache and RAM and average execution speed. More recent cache designs also consider energy efficiency, fault tolerance, and other goals. Researchers have also explored use of emerging memory technologies such as eDRAM (embedded DRAM) and NVRAM (non-volatile RAM) for designing caches.

Note: Flash memory is a specific type of EEPROM (Electrically Erasable Programmable Read-Only Memory) and is slow so it is not used as cache memory.