SRPn

SRPn is a collective name for a family of interleaved Signed-Rotate-Prefetch (SRP) instructions used in central processing units (CPUs) since Intel's Sandy Bridge and later microarchitectures. These instructions are designed to improve the throughput of data-intensive applications, such as servers and databases.

The SRP instruction set includes several variants: SRPRS (Signed Rotate Prefetch Scalar), SRPR (Signed Rotate Prefetch Register), and SRPS (Signed Rotate Prefetch Scalar Streaming). The first two are used to rotate the low-order bits of a register and prefetch data from memory, while the third variant is used for stream instructions.

In an SRP operation, the CPU executes the following steps:

1. Rotate the low-order bits of the source register left.

2. Increment an address register by the original value of the low-order bits.

3. Prefetch data from the new address location.

When a third operand is supplied, the prefetch operation can be executed without the first two steps. The new address location is calculated using this third operand and the original low-order bits.

SRP instructions are used for data-intensive tasks, enhancing the CPU's memory-reading capabilities and data management efficiency. This family of instructions offers lower latency and higher throughput, making them crucial for server workloads and database applications.

The use of SRPn instructions, particularly SRPR and SRPS, has seen widespread adoption in modern high-performance computing environments, particularly servers and servers-oriented workloads.