Monday, January 22nd 2024
Intel 15th-Generation Arrow Lake-S Could Abandon Hyper-Threading Technology
A leaked Intel documentation we reported on a few days ago covered the Arrow Lake-S platform and some implementation details. However, there was an interesting catch in the file. The leaked document indicates that the upcoming 15th-Generation Arrow Lake desktop CPUs could lack Hyper-Threading (HT) support. The technical memo lists Arrow Lake's expected eight performance cores without any threads enabled via SMT. This aligns with previous rumors of Hyper-Threading removal. Losing Hyper-Threading could significantly impact Arrow Lake's multi-threaded application performance versus its Raptor Lake predecessors. Estimates suggest HT provides a 10-15% speedup across heavily-threaded workloads by enabling logical cores. However, for gaming, disabling HT has negligible impact and can even boost FPS in some titles. So Arrow Lake may still hit Intel's rumored 30% gaming performance targets through architectural improvements alone.
However, a replacement for the traditional HT is likely to come in the form of Rentable Units. This new approach is a response to the adoption of a hybrid core architecture, which has seen an increase in applications leveraging low-power E-cores for enhanced performance and efficiency. Rentable Units are a more efficient pseudo-multi-threaded solution that splits the first thread of incoming instructions into two partitions, assigning them to different cores based on complexity. Rentable Units will use timers and counters to measure P/E core utilization and send parts of the thread to each core for processing. This inherently requires larger cache sizes, where Arrow Lake is rumored to have 3 MB of L2 cache per core. Arrow Lake is also noted to support faster DDR5-6400 memory. But between higher clocks, more E-cores, and various core architecture updates, raw throughput metrics may not change much without Hyper-Threading.
Source:
3DCenter.org
However, a replacement for the traditional HT is likely to come in the form of Rentable Units. This new approach is a response to the adoption of a hybrid core architecture, which has seen an increase in applications leveraging low-power E-cores for enhanced performance and efficiency. Rentable Units are a more efficient pseudo-multi-threaded solution that splits the first thread of incoming instructions into two partitions, assigning them to different cores based on complexity. Rentable Units will use timers and counters to measure P/E core utilization and send parts of the thread to each core for processing. This inherently requires larger cache sizes, where Arrow Lake is rumored to have 3 MB of L2 cache per core. Arrow Lake is also noted to support faster DDR5-6400 memory. But between higher clocks, more E-cores, and various core architecture updates, raw throughput metrics may not change much without Hyper-Threading.
100 Comments on Intel 15th-Generation Arrow Lake-S Could Abandon Hyper-Threading Technology
Honestly, getting rid of HT seems weird. It doesn’t really have any major downsides and leaving any performance on the table is unlike Intel. Unless they are THAT sure that the new approach will compensate and more?
Ahem
What kind of hardware issue would lead to disabling of HT ?
Intel already had weak server CPU product line right now and they are disabling HT in their next architecture?
They know they can't compete in efficiency with the new process optimized 4c cores so they "invent" this instead to try and derail the AMD CPU train.
Low IPC E cores
Constant refreshes
Lower IPC on MTL
No HT
Low core counts on Xeon
Glacial GPU development
I’m not sure Intel is really trying anymore with its chip designs.
That said, I'm not sure why this requires HT to go away; it feels like something that should be fixed at the scheduling level, not by completely reworking some very fundamental ways in which cores have been designed for over a decade. But considering how much pain scheduling over P- and E-cores has given Intel so far (WRT having both the CPU and OS having to be aware of which cores to schedule tasks to), they may have determined that this rather drastic approach - which seems to imply moving scheduling out of the operating system and fully back onto the CPU - is worth it.
Finally, it is important to remember that this is just one of hundreds of patents that Intel files every year - it absolutely does not mean this is the path their future CPUs will take.