The UltraSPARC T1 had 4-way SMT, and its successors bumped that to 8-way. Modern GPU compute is also highly based on hardware multi-threading as a way of compensating for memory latency, while also having wide execution units that can extract fine-grained parallelism within individual threads.
Also, IBM POWER have SMT at levels above 2; at least POWER 7 had 4-way SMT ("hyperthreading").
Missed that. That's part of IBM mainframe technology, where you can have "logical partitions", a cluster on a chip, and assign various resources to each. IBM POWER10 apparently allows up to 8-way hyperthreading if configured that way.
Re:Why choose async/await over threads?
by temporarely on Monday March 25, 2024 @01:56PM
(#39819380)
Thanks, very informative.
That's what "hyper-threading" is. There's enough duplicated hardware that beyond 2 hyper-threads, it seems to be more effective to add another CPU. If anybody ever built a 4-hyperthread CPU, it didn't become a major product.
It's been tried a few times in the past, back when CPUs were slow relative to memory. There was a National Semiconductor microprocessor where the state of the CPU was stored in main memory, and, by changing one register, control switched to another thread. Going way back, the CDC 6600, which was said to have 10 peripheral processors for I/O, really had only one, with ten copies of the state hardware.
Today, memory is more of a bottleneck that the CPU, so this is not a win.