Arm is so, so over this AI accelerator unit craze
Analysis Arm this week announced the availability of new top-end CPU and GPU designs ready made for system-on-chips for laptops, smartphones, and similar personal electronics. These cores are expected to power next-gen Android phones, at least, by late 2024.
The announcements touched a range of topics, some obvious from the marketing; some not. Here are the main takeaways in our view.
Arm announced the 64-bit Armv9.2 Cortex-A925 CPU core that succeeds last year's Cortex-X4. The X925 can be clocked up to 3.8GHz, can target 3nm process nodes, and according to Arm executes instructions at least roughly 15 percent faster than the X4 on a level-playing field.
We're told the CPU has various architectural improvements, such as double the L1 instruction and data cache bandwidth, a doubled instruction window size, better prefetching and branch prediction – key drivers of performance – and wider microarchitecture (eg, four rather than three load pipelines, double the integer multiplication execution, and increased SIMD/FP issue queues). All the stuff CPU designers get excited about. The key thing for users is that Arm believes devices powered by the X925 will in real-world use get a 36 percent increase in peak single-core performance over last year's hardware, dropping down to about a 30 percent average uplift in performance across a mix of workloads.
The X925 is intended to be the main beefy application core or cores in a big.Little CPU cluster of up to 14 cores total in future devices. How that cluster is configured is up to the system-on-chip designer that licenses this tech from Arm. The other CPU cores in the cluster can be the new mid-range Cortex-A725 and the smaller, efficient A520. The X925 can have up to a 3MB private L2 cache, while the A725 can go to 1MB L2. The cluster management system has been tuned to provide energy savings, too, we're told.
