3 ms·
I'm not knowing how much of this things are true, but isn't it ironic that AMD has more benefits from SMT because they have less pipeline optimizations (and sim
by dathinab 6y ago
I'm not knowing how much of this things are true, but isn't it ironic that AMD has more benefits from SMT because they have less pipeline optimizations (and similar), but exactly this pipeline optimizations (and similar) seem to be at least partially at fault for some of the Specter style attacks and make it harder to put more cores into the system (as this additional optimizations are likely need more silicon space...).
Sometimes I'm wondering if the best (but software side maybe impractical) design for (non Threadripper level) consumer PC's would be something along the line of.
- 1 single non SMT core with most advanced pipeline optimizations and highest clock speed which only always runs one thread pinned to it (many consumers tend to only run one "costy" applications with need for highest performance at the same time, e.g. a game main event loop).
- around this 4+ SMT enabled cores which are (mostly/reasonably) specter save and have less max. clock speed (other open applications, other threads from the current game, should be good enough for most applications)
- 1+ very low power cores which might have another arch (for the background maintenance tasks of the OS and programs like e.g. update jobs, slow long polling, always-on/connected features etc.)
- 1+ crypto core with integrated hardware security module, used to thinks like signing AES keys and similar (e.g. setup but not run TLS)
Through it's probably unrealistic as e.g. thermal regulations for high speed threads is optimized by "bouncing" the logical thread between cores and software
tends to not want to do things like write the background maintenance code for a different arch then the rest of the software, well phone OS probably could force this. Microsoft + Intel kinda can't.
- Scaless 6y agoYou are more or less describing the architecture of the PlayStation 3: https://en.wikipedia.org/wiki/PlayStation_3_technical_specifications#Central_processing_unit https://en.wikipedia.org/wiki/PlayStation_3_technical_specif... The problem with this type of system is both the software and OS have to be aware of what is or isn't a "main thread" job. You have to architect your whole program around job systems to spread your data between the main thread and sub-processes which was a major complaint of gamedevs for the PS3. There's also the fact that many consumer software developers just don't care and will flag all of their processes as high priority jobs. It worked out decently well on PS3 because it was such a locked down system, but for a general purpose desktop it would be utter chaos.
- inawarminister 6y agoWasn't Linux installable in early PS3s, and some labs (US military?) used stacks of PS3s as distributed superishcomputers? I wonder if anyone had analysed general computing performance in CELLs...
- princekolt 6y agoThat's what Apple's CPUs do. They have high-power cores for expensive tasks and low-power cores for background tasks and to run the device while it is locked. It's unclear at this point if they'll keep using asymmetric cores in their desktop-class CPUs, but I don't see why not. Their kernel already supports it, and the benefits are there, especially for low-power use. I can't wait for real-world usage benchmarks of their ARM CPUs once actual production machines are out in the hands of actual customers. It has the potential to upend the entire laptop market.
- flyinghamster 6y agoMost (all?) recent Qualcomm Snapdragons have exactly such small, low-power cores to handle background work. Extending that further is interesting, though it presents some tricky scheduling problems for the operating system.
- fomine3 6y agoIntel's latest Comet Lake supports per-core HT enable/disable, and supports per-core frequency long before. But I don't know how it works well by cooperating to OS