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New SiFive RISC-V core P650 with 40% IPC increase
- snvzz 5y agoSome context: RISC-V Summit is next week, and RISC-V international has just approved a batch of important extensions[0]. With these extensions, RISC-V is not missing anything relative to ARM and x86 ISAs in terms of functionality. I expect a lot of tape-outs to happen this month, as core vendors were probably holding for the announced ratifications, in fear of last minute changes. Next year is going to be exciting. [0]: https://riscv.org/announcements/2021/12/riscv-ratifies-15-new-specifications/ https://riscv.org/announcements/2021/12/riscv-ratifies-15-ne...
- socialdemocrat 5y agoThat is great news! Is there any friendly intro/coverage anywhere of the new vector extension? I am curious about the final design. Would be interesting to hear how people think it compares with ARMs scalable vector extensions.
- snvzz 5y agoThere's been a few talks on the topic. They're archived in e.g. youtube. I like it. It's fairly simple and clean, yet powerful. There was also some discussion here in HN months ago, about an article comparing RISC-V V extension and ARM SVE. The article itself got several things wrong about V, but the discussion[0] was interesting. [0] https://news.ycombinator.com/item?id=27063748 https://news.ycombinator.com/item?id=27063748
- deleted 5y ago[deleted]
- sdbbp 5y agoThis in-depth presentation is good: https://www.youtube.com/watch?v=oTaOd8qr53U https://www.youtube.com/watch?v=oTaOd8qr53U
- monocasa 5y agoI wouldn't say RISC-V isn't missing anything. The lack of add/subtract with carry is an issue for efficient runtime of many JITed languages like JavaScript. That being said, I don't think it's the worse thing in the world like some do. The focus now should be on compiled code since JITs by definition can make runtime descions on if some future extension that fixes this deficiency exists or not. The J extension has stalled for the moment, but with these other extensions ratified there should be more bandwidth available hopefully.
- rwallace 5y agoI'm curious, why do you think JavaScript wants add with carry?
- teruakohatu 5y agoCan't vendor's making desktop/mobile class CPUs detect the equivalent pattern and optimize it in microcode or silicon? Or is that what we are trying to get away from?
- monocasa 5y agoMaybe, but it's a leap, IMO. The equivalent patterns are 3x as long, and modify tons of arch visible state for their intermediate results which leaves more work for those combined instructions to do. The complaint is valid, IMO, and would show up on the filtration test they used to come up with ops if they were working with JITs too rather than just what's in AOT code.
- userbinator 5y agoIt can try... but you're basically trying to "decompile" or "compress" code to a higher level, and that's not easy nor efficient. If something relatively simple like ADC is difficult, think of something like an entire encryption/hash round, which competing CISC processors already have dedicated instructions for. In the case that you do manage to make that work, there's still the matter of those extra instructions taking up valuable space in caches and memory bandwidth. Hence why I don't think "RISC is the future" unlike a lot of other proponents; I think a CISC with uop-based decoding will be more scalable and performant. Even ARMs have moved a little in that direction.
- deleted 5y ago[deleted]
- danielEM 5y agoOnce it gets to the shelfes at reasonable price will be happy to work with/on it. Curious how IP pricing compares to ARM in this case and how much would I need to put on top of it to tape out own batch of processors
- snvzz 5y agoThe license to the ISA itself is free. There's several vendors besides RISC-V offering cores for licensing. There's even some OSHW cores that can be freely used. Even if we choose to ignore the technical prowess of being a true 5th generation RISC ISA built with hindsight no other ISA has, what's IMHO a big deal in RISC-V is the mere availability of this market of cores. It poses a threat to ARM's business model, where ARM licenses cores and ISA, but nobody else than ARM can license cores to others.
- fartcannon 5y agoSo I guess we should expect to hear a lot of FUD about RISC-V over the coming years.
- snvzz 5y agoThis is a real possibility, albeit a sad one. No amount of FUD will save ARM. Only pivoting into a different business model could.
- duskwuff 5y agoHonestly, ARM is fine. They're no longer the only game in town, but they've still got a huge head start.
- snvzz 5y agoThey'll be fine if they focus on their microarchitectures rather than the ISA (where IMHO they've already lost), and make the process for obtaining a license much more streamlined; I've heard it takes no less than 18 months of long negotiations to license anythin from ARM. That's not sustainable now that there's competition.
- socialdemocrat 5y agoAnyone able to put this in context? How fast are these cores compared to various ARM, Intel and AMD cores? At what level can they compete?
- sebow 5y agoIf i recall correctly the sifive unmatched is still pretty slow compared to ARM( https://www.phoronix.com/scan.php?page=article&item=hifive-unmatched-benchmarks&num=1 https://www.phoronix.com/scan.php?page=article&item=hifive-u... ).Now this board is not the one in question(P650) but we'll have to observe upcoming benchmarks [for which i recommend phoronix] Obviously you can't even think about comparing it further with Intel & AMD, but when you look at the history of something like ARM(which i believe is 30-40 years old), riscv came a long way pretty fast, and the good thing it's a solid choice for the future due being open.
- sanxiyn 5y ago> With a projected score of 11+ SPECInt2006/GHz, the SiFive Performance P650 brings RISC-V into a new category of high-end computing applications. 11+ SPECInt2006/GHz is comparable to Apple Icestorm microarchitecture. Apple Firestorm microarchitecture is roughly 2x better at 22 SPECInt2006/GHz.
- pantalaimon 5y agoMind you that raw core performance is not everything, memory bandwidth and caches are crucial to make sure the CPU isn't waiting for data all the time.
- sanxiyn 5y agoYes, but SPECint includes all such effects. As long as SPECint benchmarks (such as GCC) are representative of your workload, it works fine.
- tlb 5y agoI trust that the Apple benchmarks include all such effects. I'm less convinced that the RISC-V "projections" include them. SPECint2006 is supposed to be measured with real memory and an OS. Per-GHz numbers can't accurately reflect main memory latency, since its speed doesn't scale with the CPU clock.
- sebow 5y agoSweet, are there any resources on transitioning/migrating or differences between x86_64 and riscv; or the ISAs are drastically different that it's just better to dive in head-first?
- ruslan 5y agoIt's same as x86_64 vs aarm64. If you feel comfortable with aarm64, switching to RV64 will go without a notice. Note, that switching to ARM from x86 is a pain, esp if you depend on proprietary software.
- Epiphany21 5y agoI played with Linux (Debian) for RV64 in Qemu and the experience was pretty painless, albeit slow but I think that was more to do with emulation overhead. My personal programs I wrote myself compiled and ran without a single issue. Obviously if you need closed source software or software with build tools targeting an OS that doesn't run on RISC-V, then yeah you would have a hard time. Most open source software should be a breeze to port. A lot of the weirdness of the platform will likely be from bootloaders and drivers.
- ruslan 5y agoAbsolutely. If you can go with OSS only, than it's easy as a breeze. Yet if you depend on proprietary stuff like I do (CADs, Wine, etc), than it's a pain. I'm currently trying to switch office to ARM (RPi 4 and Baikal-M) and that is not easy.
- baybal2 5y agoThis is something genuinely interesting from riscv crowd for the first time
- bruce343434 5y ago> With a projected score of 11+ SPECInt2006/GHz That seems to imply a certain integer arithmetic performance, but I wonder what the floating point performance is. They could have just said "X flops". Comparing to other benchmarks at [1], I have no idea, because they all have denormalized results, so totals, rather than per GHz per core. Nice reporting. How fast is this thing? Pentium? first gen i3? current gent ryzen 5? The fact that they are being so obtuse about it leads me to believe performance isn't great. [1] https://www.spec.org/cgi-bin/osgresults?conf=cint2006;op=dump;format=pre https://www.spec.org/cgi-bin/osgresults?conf=cint2006;op=dum...
- wmf 5y agoI'd compare it to an Atom "efficiency" core.
- DeathArrow 5y agoA little lower than Pentium 4 640.
- marcodiego 5y agoFaster than ARM A-77: https://www.phoronix.net/image.php?id=2021&image=sifive_p650_1_show https://www.phoronix.net/image.php?id=2021&image=sifive_p650... . Performance comparable to Apple Icestorm architecture, the 'efficiency' cores in M1. Considering A-710 is the fastest ARM core currently available and its successor will only be available next year, SiFive is just a few years before real competition starts in an arena currently dominated by ARM. This will be beautiful to watch.
- deleted 5y ago[deleted]
- zozbot234 5y agoIt will be interesting to see a comparison on power-efficiency as well as performance. RISC-V implementations have shown a pretty sizeable advantage wrt. power use in the past, and we don't quite know how this advantage compares in these larger, performance-focused designs.
- DeathArrow 5y agoPower efficiency and performance depends very much on process node. If Apple bought all future 3nm capacity from TSMC, good luck trying to compete.
- dmitrygr 5y ago> just a few years before real competition starts Are you assuming the competition will just sit and do nothing?
- GhettoComputers 5y agoGood enough” matters more than benchmarks. They can make supercomputers but it doesn’t matter to someone who wants a $100 computer.
- dmitrygr 5y ago
- jaas 5y agoWho exactly are the customers for this chip?
- ruslan 5y agoThe press-release does not say anything about physical chip, but a licensable core that can be used to build SoCs. Here SiFive acts same way as ARM does - sells cores.
- DeathArrow 5y agoWe expected new developments since ages ago. I guess the RISC-V will conquer the desktop the same year Linux will.