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But RISC-V predates loongarch64 - why did Loongson create a new ISA instead of implementing a fast RISC-V core? Sure you can move faster if you can make your o

But RISC-V predates loongarch64 - why did Loongson create a new ISA instead of implementing a fast RISC-V core? Sure you can move faster if you can make your own standards and don't have to coordinate with anyone, but still makes me wonder if there is some fundamental issue that makes it difficult to create a high performance RISC-V implementation.

rwmj 1y ago
How does it compare to the current RISC-V leader, ESWIN SiFive P550? Anyway, China seem to have decided to pursue a dual strategy of pouring money into RISC-V and LoongArch at the same time. I've no idea why that is. The company I work for talks to several RISC-V vendors who don't believe there is any issue with the RISC-V ISA for high performance server-class application cores.
- pantalaimon 1y ago
  > How does it compare to the current RISC-V leader, ESWIN SiFive P550? I couldn't find many benchmarks of the P550, but at Phoronix it got beaten by a Raspberry Pi 4 https://www.phoronix.com/review/sifive-hifive-premier-p550 https://www.phoronix.com/review/sifive-hifive-premier-p550 which the 3A6000 beats easiely https://openbenchmarking.org/vs/Processor/Loongson-3A6000,ARMv8+Cortex-A72+4-Core https://openbenchmarking.org/vs/Processor/Loongson-3A6000,AR...
- adgjlsfhk1 1y ago
  The P550 is pretty slow. It doesn't have any SIMD, and it's scalar engine is ~about the same as a Core 2 from ~2008. In general, it's fairly confusing to me why SciFive has been so cautious in their designs. It seems like they would be in a much better place if they'd released a few CPUs where rather than trying to balance everything while creeping complexity up, they just added all the power to theoretically match high end CPUs and then addressed the bottlenecks over iterations.
  - brucehoult 1y ago
    > The P550 is pretty slow. It doesn't have any SIMD, and it's scalar engine is ~about the same as a Core 2 from ~2008. Yes! And this is great progress in just a couple of years. The previous SiFive core that made it to available hardware, the U74, is about like a Pentium or PowerPC 603 in µarch, though with higher clock speed so putting it more like late Pentium 3 or PowerPC G4 in delivered performance (and also quad core, not single core, which helps a lot). SiFive already have 2 1/2 generations of core released since the P550 in mid 2021, the P670 and the P870(-D). Both of those implement RVV (Vector). If not for US sanctions we'd be seeing very nice 16x P670 machines this year, likely quite a bit better than the Pi 5 (and Rock 5 and Orange Pi 5). Or somewhere between Sandy Bridge and Skylake in Intel terms, I think. The P870 is somewhere around Snapdragon 8 gen 2. It just takes time to get CPU cores from the drawing board to shops, and especially for a company that wants to make consumer products to license the core in the first place since SiFive (like Arm) doesn't make chips. RISC-V is behind Arm, but the gap in cores available to license is far smaller (about 2 years at present) than the gap in things anyone can buy in a shop (about 5 years at present) and getting smaller all the time. > it's fairly confusing to me why SciFive has been so cautious in their designs. It seems like they would be in a much better place if they'd released a few CPUs where rather than trying to balance everything while creeping complexity up, they just added all the power to theoretically match high end CPUs Because most of the market (by volume / revenue / profit) does not need the highest end CPUs. Even in phones the Galaxy S25, with its Qualcomm Oryon cores, is a nice headline product, but there are still new SoCs and phones being introduced today (or at least there were some in February 2024 ... I haven't checked recently) with nothing faster than Arm A53 cores announced in 2012. I expect those low end phones are still selling in pretty big numbers.
    - adgjlsfhk1 1y ago
      > Yes! And this is great progress in just a couple of years. Is it? In 5 years they went from the HiFive Unmatched on 5nm (Intel ~1999 except missing vector instructions so it's ~4x slower) to the HiFive Premier on 7nm (~Intel 2008 except it's still missing vector instructions so it's ~4x slower on a lot more things). Sure that means they're catching up, but it really seems like they should be further along since they don't need anything "new", they can just take the ratios of a 5 year old CPU and build that. The P650 to me seems like the first of their CPUs that will be of a moderately reasonable performance level, but due to sanctions it's unclear when/if it will ever launch in a dev board. > Because most of the market (by volume / revenue / profit) does not need the highest end CPUs. The problem is that any new ISA that wants to compete in the general purpose market needs some high power CPUs if only to give developers something to play with/run CI/compile the world on. They don't need to develop on a new node, they don't need to be ultra power or cost efficient, etc. They just need a chip with some moderately OK power. If they had by now a dev board that was $2000, consumed 300w and crashed if you looked at it funny, that would be better than what we have now, because their current products don't include anything that runs faster than QEMU.
hajile 1y ago
Loongarch is built on MIPS, so the core predates RISC-V by decades. RISC-V didn't have the specs to build what they were targeting when they started designing a few years ago. Given the similarities in the ISAs, I suspect they may switch to RISC-V in the near future.
MisterTea 1y ago
> why did Loongson create a new ISA instead of implementing a fast RISC-V core? Simple: They're a MIPS shop.

rwmj 1y ago

How does it compare to the current RISC-V leader, ESWIN SiFive P550? Anyway, China seem to have decided to pursue a dual strategy of pouring money into RISC-V and LoongArch at the same time. I've no idea why that is. The company I work for talks to several RISC-V vendors who don't believe there is any issue with the RISC-V ISA for high performance server-class application cores.

pantalaimon 1y ago
> How does it compare to the current RISC-V leader, ESWIN SiFive P550? I couldn't find many benchmarks of the P550, but at Phoronix it got beaten by a Raspberry Pi 4 https://www.phoronix.com/review/sifive-hifive-premier-p550 https://www.phoronix.com/review/sifive-hifive-premier-p550 which the 3A6000 beats easiely https://openbenchmarking.org/vs/Processor/Loongson-3A6000,ARMv8+Cortex-A72+4-Core https://openbenchmarking.org/vs/Processor/Loongson-3A6000,AR...
adgjlsfhk1 1y ago
The P550 is pretty slow. It doesn't have any SIMD, and it's scalar engine is ~about the same as a Core 2 from ~2008. In general, it's fairly confusing to me why SciFive has been so cautious in their designs. It seems like they would be in a much better place if they'd released a few CPUs where rather than trying to balance everything while creeping complexity up, they just added all the power to theoretically match high end CPUs and then addressed the bottlenecks over iterations.
- brucehoult 1y ago
  > The P550 is pretty slow. It doesn't have any SIMD, and it's scalar engine is ~about the same as a Core 2 from ~2008. Yes! And this is great progress in just a couple of years. The previous SiFive core that made it to available hardware, the U74, is about like a Pentium or PowerPC 603 in µarch, though with higher clock speed so putting it more like late Pentium 3 or PowerPC G4 in delivered performance (and also quad core, not single core, which helps a lot). SiFive already have 2 1/2 generations of core released since the P550 in mid 2021, the P670 and the P870(-D). Both of those implement RVV (Vector). If not for US sanctions we'd be seeing very nice 16x P670 machines this year, likely quite a bit better than the Pi 5 (and Rock 5 and Orange Pi 5). Or somewhere between Sandy Bridge and Skylake in Intel terms, I think. The P870 is somewhere around Snapdragon 8 gen 2. It just takes time to get CPU cores from the drawing board to shops, and especially for a company that wants to make consumer products to license the core in the first place since SiFive (like Arm) doesn't make chips. RISC-V is behind Arm, but the gap in cores available to license is far smaller (about 2 years at present) than the gap in things anyone can buy in a shop (about 5 years at present) and getting smaller all the time. > it's fairly confusing to me why SciFive has been so cautious in their designs. It seems like they would be in a much better place if they'd released a few CPUs where rather than trying to balance everything while creeping complexity up, they just added all the power to theoretically match high end CPUs Because most of the market (by volume / revenue / profit) does not need the highest end CPUs. Even in phones the Galaxy S25, with its Qualcomm Oryon cores, is a nice headline product, but there are still new SoCs and phones being introduced today (or at least there were some in February 2024 ... I haven't checked recently) with nothing faster than Arm A53 cores announced in 2012. I expect those low end phones are still selling in pretty big numbers.
  - adgjlsfhk1 1y ago
    > Yes! And this is great progress in just a couple of years. Is it? In 5 years they went from the HiFive Unmatched on 5nm (Intel ~1999 except missing vector instructions so it's ~4x slower) to the HiFive Premier on 7nm (~Intel 2008 except it's still missing vector instructions so it's ~4x slower on a lot more things). Sure that means they're catching up, but it really seems like they should be further along since they don't need anything "new", they can just take the ratios of a 5 year old CPU and build that. The P650 to me seems like the first of their CPUs that will be of a moderately reasonable performance level, but due to sanctions it's unclear when/if it will ever launch in a dev board. > Because most of the market (by volume / revenue / profit) does not need the highest end CPUs. The problem is that any new ISA that wants to compete in the general purpose market needs some high power CPUs if only to give developers something to play with/run CI/compile the world on. They don't need to develop on a new node, they don't need to be ultra power or cost efficient, etc. They just need a chip with some moderately OK power. If they had by now a dev board that was $2000, consumed 300w and crashed if you looked at it funny, that would be better than what we have now, because their current products don't include anything that runs faster than QEMU.

hajile 1y ago

Loongarch is built on MIPS, so the core predates RISC-V by decades. RISC-V didn't have the specs to build what they were targeting when they started designing a few years ago. Given the similarities in the ISAs, I suspect they may switch to RISC-V in the near future.

MisterTea 1y ago

> why did Loongson create a new ISA instead of implementing a fast RISC-V core? Simple: They're a MIPS shop.