L1 Cache Memory

The Level 1 cache is the fastest cache memory on the CPU which is used for temporary storage of instructions and data organized in blocks of 32 bytes. L1 cache is also known as Primary cache which is the fastest form of storage, because it is built in to the chip with a zero wait-state (delay) interface to the processor’s execution unit.

L1 cache is limited in size. It is used to store data (critical files that need to be executed immediately) as it is the first cache to be accessed and processed when the processor itself performs a computer instruction.

The Intel’s P55 MMX processor, launched in 1997, was in size of its Level 1 cache to 32KB. The AMD K6 and Cyrix M2 chips launched later in that year, provided Level 1 caches of 64KB. 64KB remained the standard L1 cache size.

In recent microprocessors, the L1 cache is divided equally into two cache : one cache to keep program data and another cache to keep instructions for the microprocessor. On other hand, some older microprocessors used undivided L1 cache which stored both program data and microprocessor instructions.

Level 1 cache is being implemented by Static RAM (SRAM). SRAM uses two transistors per bit that hold data without external assistance, till the power is supplied to the circuit. The second transistor controls the output of the first transistor. The two transistor forms a circuit known as a flip-flop because it has two stable states which it can flip between. This is contrasted to dynamic RAM (DRAM), which must be refreshed regularly per second in order to hold its data contents.