5 ms·

Derbauer pointed out that, for Intel's 12 series, that the e-cores dominate the p-cores not just in performance per watt, but also performance-per-die-area. I

by xmodem 5y ago

Derbauer pointed out that, for Intel's 12 series, that the e-cores dominate the p-cores not just in performance per watt, but also performance-per-die-area. I haven't run the numbers for the M1, but I'd be shocked if it wasn't similar. It seems unavoidable that you can get more total performance with larger numbers of slower cores than smaller numbers of faster cores. The silicon industry has spent the entire multi-core era - the last 15 years - fighting this reality, but it finally seems to have caught up with us, so hopefully in the next few years we will start to see software actually start to adapt.

hajile 5y ago
It's pretty well established that M1 E-cores are something like 50% the performance, but 1/10 the power consumption. A55 is probably 1/8 the performance, but something like 1/100 of the power consumption and a miniscule die area. I wouldn't want to have all A55 cores on my phone though. Performance per die area is also relative. For example, Apple clocks their chips around 3GHz. If they redesigned them so they could ramped them up to 5GHz like Intel or AMD, they would stomp those companies, but they would also use several times more power. What is really relevant is something like the ratio of a given core's performance per area per watt to the same value for the fastest known core. The only interesting area for ultimate low-power in general purpose computing is some kind of A55 with a massive SIMD unit going with a larabee-style approach for a system that can both do massive compute AND not have performance plummet if you need branchy code too.
- paulmd 5y ago
  Apple's e-cores are actually (relatively speaking) much better than Intel's. From memory, Apple gets about the same performance (actually higher in single-threaded, but same MT performance) out of about 2/3rds the transistor count as Intel. Note that this is invariant of node - obviously Blizzard cores are physically much smaller than Gracemont, but they are more smaller than you get out of a node shrink alone, apple is doing more with actually less transistors than Intel. Since the Intel e-cores still have a relatively wide decoder, e-core designs may be the part where the bill comes due for x86 in terms of decoder complexity. Sure it's only 3% of a performance core, but if you cut the performance core in half then now they're 6%. And the decoder doesn't shrink that much, Gracemont has a 3-wide decoder vs 4-wide on Golden Cove, and you still have to have the same amount of instruction cache (instruction cache hit rate depends on the amount of "hot code", and programs don't get smaller just because you run them on e-cores). A lot of the x86 "tricks" to keep the cores fed don't scale down much/any. edit: Intel Golden Cove: 7.04mm^2 with L2, 5.55mm^2 w/o L2 Intel Gracemont: 2.2mm^2 with L2, 1.7 mm^2 w/o L2 Apple Avalanche: 2.55mm^2. (I believe these are both w/o cache) Apple Blizzard: 0.69mm^2 (nice) Note that N7 to N5 has roughly 1.6x logic density scaling - so a Blizzard core would be 1.24mm^2 or roughly 73% of the transistor count of Gracemont for equivalent performance! For the p-cores the number is 82%. This is one of the reasons I feel Apple is so far ahead. It's not about raw performance, or even efficiency, it's the fact that Apple is winning on both those metrics while using 2/3rds the transistors. It's not just "apple throwing transistors at the problem", which of course they are, but just they're starting from a much better baseline such that they can afford to throw those transistors around. The higher transistor count in total is coming from the GPU, the cores themselves Apple is actually much more efficient (perf-per-transistor) than x86 competitors.
  - hajile 5y ago
    Golden Cove has 6-wide decoders (that should be using massive amounts of resources). Of course, it doesn't help that Intel lists laptop chip turbo frequencies to use either 95w or 115w and Anandtech's laptop review of one had the 12900H hitting those numbers with sustained power draw at an eye-raising 85w. That's 2-3x the power of M1 Pro and only 20-30% more performance. That laptop also showed that cutting power from 85w to 30w roughly halved the performance. On the plus side, this means their power scaling is doing pretty well. On the negative side of things, it means their system gets worse multithreaded performance at 30w despite having 40% more cores.
BackBlast 5y ago
That's not the only factor at play. Many to most applications are dominated by single thread performance. JavaScript's interpreters are single threaded, for example. Something I don't often see, but it does come up here and there. One nice thing about the M1 is the performance is consistent as it doesn't have a massive auto-scaling boost involved. An Intel or AMD chip might start off at top speed single thread, but then something else spins up on another core, and you take a MHz hit on your primary thread to keep your TDP in spec. The background task goes away, and the MHz goes back up. Lots of performance jitter in practical use. Interconnects and IO also consume power. You can't just scale small e-core counts without also hitting power walls there too. All that said, I'd love to see some E-core only chips come out of intel targeted at thin clients and long battery life notebooks.
- paulmd 5y ago
  > All that said, I'd love to see some E-core only chips come out of intel targeted at thin clients and long battery life notebooks. they exist, that's called Atom. "e-core" is just a rebranding of Atom because the Atom brand is toxic with a huge segment of the tech public at this point, but Gracemont is an Atom core. There's no Gracemont-based SKUs yet, but Tremont-based Atoms exist (they're in one of the models of NUC iirc), which is the generation before. Also, the generation before that is Goldmont/Goldmont Plus which are in numerous devices - laptops, thin clients, and NUCs. Keep an eye on the Dell Wyse thin-client series, there are a lot of Goldmont-based units available if you can settle for a (low-priced surplus) predecessor.
  - BackBlast 5y ago
    I have a Dell Wyse, I'm familiar with them. Intel has generally gimped Atoms. The 5070 is tolerable, but it would be nice to have better RAM capacity. Gracemont is such a huge departure from previous atom offerings I don't really consider them as having the same design goals. These new e-cores would be really nice for my use cases, better density and power efficiency than Ryzen. Maybe with AMD dragging their feet on the V2000 and V3000 lines of low power offerings, I can get these sooner...

by xmodem 5y ago

hajile 5y ago

It's pretty well established that M1 E-cores are something like 50% the performance, but 1/10 the power consumption. A55 is probably 1/8 the performance, but something like 1/100 of the power consumption and a miniscule die area. I wouldn't want to have all A55 cores on my phone though. Performance per die area is also relative. For example, Apple clocks their chips around 3GHz. If they redesigned them so they could ramped them up to 5GHz like Intel or AMD, they would stomp those companies, but they would also use several times more power. What is really relevant is something like the ratio of a given core's performance per area per watt to the same value for the fastest known core. The only interesting area for ultimate low-power in general purpose computing is some kind of A55 with a massive SIMD unit going with a larabee-style approach for a system that can both do massive compute AND not have performance plummet if you need branchy code too.

paulmd 5y ago
Apple's e-cores are actually (relatively speaking) much better than Intel's. From memory, Apple gets about the same performance (actually higher in single-threaded, but same MT performance) out of about 2/3rds the transistor count as Intel. Note that this is invariant of node - obviously Blizzard cores are physically much smaller than Gracemont, but they are more smaller than you get out of a node shrink alone, apple is doing more with actually less transistors than Intel. Since the Intel e-cores still have a relatively wide decoder, e-core designs may be the part where the bill comes due for x86 in terms of decoder complexity. Sure it's only 3% of a performance core, but if you cut the performance core in half then now they're 6%. And the decoder doesn't shrink that much, Gracemont has a 3-wide decoder vs 4-wide on Golden Cove, and you still have to have the same amount of instruction cache (instruction cache hit rate depends on the amount of "hot code", and programs don't get smaller just because you run them on e-cores). A lot of the x86 "tricks" to keep the cores fed don't scale down much/any. edit: Intel Golden Cove: 7.04mm^2 with L2, 5.55mm^2 w/o L2 Intel Gracemont: 2.2mm^2 with L2, 1.7 mm^2 w/o L2 Apple Avalanche: 2.55mm^2. (I believe these are both w/o cache) Apple Blizzard: 0.69mm^2 (nice) Note that N7 to N5 has roughly 1.6x logic density scaling - so a Blizzard core would be 1.24mm^2 or roughly 73% of the transistor count of Gracemont for equivalent performance! For the p-cores the number is 82%. This is one of the reasons I feel Apple is so far ahead. It's not about raw performance, or even efficiency, it's the fact that Apple is winning on both those metrics while using 2/3rds the transistors. It's not just "apple throwing transistors at the problem", which of course they are, but just they're starting from a much better baseline such that they can afford to throw those transistors around. The higher transistor count in total is coming from the GPU, the cores themselves Apple is actually much more efficient (perf-per-transistor) than x86 competitors.
- hajile 5y ago
  Golden Cove has 6-wide decoders (that should be using massive amounts of resources). Of course, it doesn't help that Intel lists laptop chip turbo frequencies to use either 95w or 115w and Anandtech's laptop review of one had the 12900H hitting those numbers with sustained power draw at an eye-raising 85w. That's 2-3x the power of M1 Pro and only 20-30% more performance. That laptop also showed that cutting power from 85w to 30w roughly halved the performance. On the plus side, this means their power scaling is doing pretty well. On the negative side of things, it means their system gets worse multithreaded performance at 30w despite having 40% more cores.

BackBlast 5y ago

That's not the only factor at play. Many to most applications are dominated by single thread performance. JavaScript's interpreters are single threaded, for example. Something I don't often see, but it does come up here and there. One nice thing about the M1 is the performance is consistent as it doesn't have a massive auto-scaling boost involved. An Intel or AMD chip might start off at top speed single thread, but then something else spins up on another core, and you take a MHz hit on your primary thread to keep your TDP in spec. The background task goes away, and the MHz goes back up. Lots of performance jitter in practical use. Interconnects and IO also consume power. You can't just scale small e-core counts without also hitting power walls there too. All that said, I'd love to see some E-core only chips come out of intel targeted at thin clients and long battery life notebooks.

paulmd 5y ago
> All that said, I'd love to see some E-core only chips come out of intel targeted at thin clients and long battery life notebooks. they exist, that's called Atom. "e-core" is just a rebranding of Atom because the Atom brand is toxic with a huge segment of the tech public at this point, but Gracemont is an Atom core. There's no Gracemont-based SKUs yet, but Tremont-based Atoms exist (they're in one of the models of NUC iirc), which is the generation before. Also, the generation before that is Goldmont/Goldmont Plus which are in numerous devices - laptops, thin clients, and NUCs. Keep an eye on the Dell Wyse thin-client series, there are a lot of Goldmont-based units available if you can settle for a (low-priced surplus) predecessor.
- BackBlast 5y ago
  I have a Dell Wyse, I'm familiar with them. Intel has generally gimped Atoms. The 5070 is tolerable, but it would be nice to have better RAM capacity. Gracemont is such a huge departure from previous atom offerings I don't really consider them as having the same design goals. These new e-cores would be really nice for my use cases, better density and power efficiency than Ryzen. Maybe with AMD dragging their feet on the V2000 and V3000 lines of low power offerings, I can get these sooner...