Say goodbye to Intel old favorite SMT " Hyper-Threading Technology " since Pentium 4 Northwood.
We all know Intel introduced a new hybrid (Performance+Efficient) architecture with Alder Lake (12th Gen). The way these cores work is easy, complex tasks are assigned by the OS to the P-Cores, whereas the E-Cores handle the background tasks.
The P-Cores have SMT enabled, but they cannot work in parallel since a physical core, even with two logical threads can only execute one instruction at once. In a sense, to overcome this problem of parallelism, Intel introduced Efficient cores which under the Rentable Unit architecture will succeed Hyperthreading.
This sounds very confusing but stay with me for a moment. We’ll use the diagram below to understand Rentable Units. The dotted line represents the total time available. A complex instruction termed ‘Task 1‘ is executed on Thread 1, the Performance Core. A similar instruction ‘Task 2‘ is presented to Thread 2, the Efficient Core.
The first task is executed in minimal time and Thread 1 is left idle. Meanwhile, the second task takes much longer. The concept here is to divide these two tasks in such a way that it keeps both Threads 1 and 2 occupied 100% of the time. So, after the P-Core does its job, it takes on the Efficient Core’s remaining chores, allowing both tasks to be completed earlier than before.
- The Rentable Unit takes instructions and divides them based on their complexity, available resources, and CPU structure.
- The Rentable Unit will then schedules these tasks across the Performance and Efficient cores, leaving no core inactive.
- The aim is to keep no core inactive, the Performance Core can complete the Efficient Core’s remaining work if it is free.
From this patent It will drive PC processor following ARM base processor in future. Hyperthreading and AVX256/512/AMX will be replace as Intel AI processor with rentable units begining from Lion Cove P-Core and Skymont E Core on LGA 1851 platform.
