3 ms·

I believe there will come a day when RISC-V has comparable or better performance than ARM and x86_64. This is based on history: I remember when x86 performance

I believe there will come a day when RISC-V has comparable or better performance than ARM and x86_64. This is based on history: I remember when x86 performance compared to the DEC Alpha, PA-RISC, SPARC, etc. was a joke. There was a time when, if you wanted real performance, you needed to pony up $20,000-$50,000 for a workstation with a MIPS/PA-RISC/SPARC/Alpha/whatever processor. All these workstations smoked the x86 computers of the era. However, people were buying x86 computers at a far higher rate, giving Intel (and AMD) the money needed to invest in better chip designs and better fabs. Linux was, at the same time, gaining traction and, around the time the dot-com bubble popped and there were no longer companies with the money needed to get Sun SPARC workstations (or what not) at $50,000 or more a pop to start up a web business, x86 computers running Linux had nearly the same performance at a much lower price. Once the Itanium sank and x86_64 was mainstream, x86_64 was the ISA of choice for performance workstations and servers, and the RISC ISAs that survived were now mainly used in the embedded space. Indeed, ARM was never a high performance RISC processor, and it was the one that took over the embedded space while PA-RISC, Alpha, and SPARC died. The ISA for what were cheap computers become the highest performance ISA around. It has been only in the 2020s that RISC processors have gotten x86_64 levels of performance, notably in the the Apple M series of processors. So now ARM, an ISA which was geared for cheap embedded devices, has become a high performance processor, in line with x86. Right now, RISC-V is mainly being used in cheap embedded components. Considering that x86 and ARM also were made for cheap computing, until becoming the dominant high end processor, history tells us that the cheapest ISA is the one which will become the highest performance one. RISC-V currently has about the same performance as a high end Raspberry Pi. I predict it will have medium-level PC performance by the end of the 2020s.

jackb4040 2mo ago
It's fascinating to me what you're describing. That ISA prevalence basically comes down to the anarchy of the market, and theoretical differences in the actual design don't really factor in. Is this true? Can we analyse the reasons we expect RISC-V to have better performance, and possibly even extrapolate that to a theoretically even better ISA and skip over RISC-V entirely?
- strenholme 2mo ago
  Getting RISC-V to have better performance is a matter of in-chip optimizations (caches, pipelines, etc.) and high quality performance oriented fabs. The dominance of x86 after the dot-com bubble popped shows that one can get incredible performance even from an ISA which is a hack on top of a hack on top of another hack. [1] In terms of a “theoretically even better ISA”, if anyone has any proposals, I would love to see links to them. In particular, the article “RISC-V: They Should Have Known Better” does not propose an ISA (except mentioning that the author feels AArch64 is much better), so I find its criticisms dubious. [1] I will make one ISA propsal: x86_64 should have had 32 instead of 16 registers, but 16 registers at least is quite a bit better than the 4-8 registers the 386 had.
  - jackb4040 2mo ago
    But is there any article / papers / field of study that explores the theoretical maximum of various architectures, given infinite resources? Do they begin to converge, such that a highly optimized Arm looks similar to a highly optimized RISC-V core? If we are near / past the point of diminishing returns for x86, how mathematically rigorous is our proof of that?
  - anon-3988 2mo ago
    > [1] I will make one ISA propsal: x86_64 should have had 32 instead of 16 registers, but 16 registers at least is quite a bit better than the 4-8 registers the 386 had. Is "registers" still a real thing or its just an illusion at this point? I am pretty sure there are "virtual" registers or micro instructions (something like that, I forgot the terminology)
    - inkyoto 2mo ago
      Registers are very much real, and their number being available at the ISA level will continue to matter regardless of the actual number of shadow registers. Being able to store, e.g. 10 vs 5, local variables in a larger register file has performance implications[0] strong enough to consider larger register files an advantage. [0] The reduced number of memory-to-CPU and vice versa data transfers for transient computation results.
inkyoto 2mo ago
Competing RISC designs tanked for a number of reasons, but not just because Intel and AMD started pumping money into their products. RISC vendors were in the business of selling hi-end workstations and servers that required their own respective RISC CPU's, which meant that each vendor had its own, in-house CPU design arm and either their own fab or they outsourced the CPU manufacturing to someone else. In a way, the RISC CPU was a by-product of what they sold but never the product they sold alone. Two problems followed. The CPU design is an expensive process, and keeping one's own fabs up to date with the latest and greatest manufacturing process is even more expensive, especially as the designs and processes advanced. It eventually became prohibitively expensive to maintain one's own fab, and RISC vendors started falling behind the bleeding edge (DEC, Motorola, etc.). IBM managed to get away with it for a time, but eventually, they also divested. The second problem concerned the outsourcing of the CPU manufacturing. Those RISC vendors (e.g. SGI with their MIPS) who did not have their own fabs had to contract a fab (e.g. NEC). Such a fab would produce a diverse range of microchip products, and a CPU would be just one of them. Which typically meant not the latest and greatest process, but at least a generation behind. Whereas both Intel and AMD were dedicated CPU design and manufacturing houses (although AMD also divested their fabs later), so they could specifically focus on what mattered for CPU's and for CPU's only. That said, for Intel and AMD, the CPU was the product, whereas for the RISC vendors, it was not, however important, the CPU was for them.
TMWNN 2mo ago
>Right now, RISC-V is mainly being used in cheap embedded components. Considering that x86 and ARM also were made for cheap computing, until becoming the dominant high end processor, history tells us that the cheapest ISA is the one which will become the highest performance one. You surely mean "history tells us that the cheapest and largest-volume ISA is the one which will become the highest performance one". It's not "RISC" having reached x86 levels; it's ARM variants. They did so with volume that for the first time in modern computing massively exceeded x86's. Apple's PA Semi acquisition has resulted in wizardry, but that wizardry would not have been possible without the massive volumes TSMC enjoys. In any case, I'm not convinced that the above is sufficient; there has to be some level of technical superiority (or at least reasonably equal-level) as well. Otherwise, some inexpensive microcontroller that is manufactured at 100X the volume of x86 would have taken off. Does RISC-V have enough "goodness" in its design? I do not know.
- hajile 2mo ago
  Here's a good one. Qualcomm beat ARM in court and reportedly pays 2-3% royalties where ARM was demanding 5-10% royalties. Qualcomm's ARM license expires around 2028 with an option to extend to 2033 (for some amount of money). If Qualcomm is locked into ARM when renewal comes up, ARM is going to not only name the higher price, but likely charge even more to recover their lost revenue. Qualcomm is already designing their own cores and ARM is charging them billions for the privilege. Increasing net profits 2-3% for simply doing the thing you are doing seems like a very easy choice. Increasing net profits 5-10% (maybe more) after the price hike seems like a fiduciary responsibility. This isn't just talk either. Qualcomm already proposed a RISC-V Znew extension (nearly 300 pages of changes to make the ISA more like ARMv8). They bought Ventana (a company already done with their second very wide RISC-V design). They partnered with other companies to make Quintauris for promoting RISC-V too. There's a non-zero chance we see a RISC-V design from Qualcomm before 2028 and I believe a near 100% certainty of a RISC-V design before 2033.
hn_submit 2mo ago
The x86 only caught up because of process technology, less so due to technological innovation (RISCifying x86 architecture). DEC, HP and MIPS simply couldn't keep up with Intel, which had its own fabs. And this was at a time when fabs-for-hire with world-leading process technology like TSMC didn't yet exist. Today, almost any fabless manufacturer can order world-class leading semiconductors from TSMC, just like Apple is doing now. Drawback is that most RISC-V manufacturers are in China, which don't have access to TSMC's manufacturing technology. And Apple is heavily invested in ARM since it owns part of the technology.
drbscl 2mo ago
> It has been only in the 2020s that RISC processors have gotten x86_64 levels of performance, notably in the the Apple M series of processors It's worth keeping in mind that modern ARM isn't really all that _RISC_, number of instructions in these chips is starting to approach x86_64 territory pretty fast
saltcured 2mo ago
It was also a messy time where software did make a lot of difference to your experience of performance. I had a few of these apples to oranges comparisons that frustrated me, as someone who absorbed the 90s counter-culture message that MS and Intel were monopolistic and needed to be displaced. In the mid 90s, I got myself a DEC Multia (small Alpha-based workstation) to run Linux. It was fast at some things, but useless to browse the newly emerging web. Netscape Navigator wasn't available as an Alpha binary, and the emulated x86 was just as slow as an early Python based browser. Running Netscape on a 486DX3-100 was night and day like visiting the future. Some other native programs went the other way, with the Alpha beating the 486 dearly. But the web browser became more and more significant. In college, I was also told I should covet Sun hardware. At my first job, I got issued a Sun Ultra workstation of some sort. I was appalled at how slow it was for my FOSS C programming workflows with autoconf/make/gcc etc. I started bringing in a Dell notebook with a Pentium-MMX running Linux, and it ran circles around the Ultra for actual day to day tasks. On the other hand, when I had to run certain commercial tools like Purify, the Sun was useful again. I also had exposure to supercomputer centers at the time, doing portability work for our HPC codebase. It was often crazy how slow these platforms were for development work. There may have been a little bit of neglect by the vendors or IT groups in terms of what hardware they dedicated as front-end service nodes on these big machines. But, there were also dramatic differneces in the operating system behavior, tuned to get one user-level job running and get out of the way. They were terrible at multitasking, and this showed through in CLI/scripted interactivity too. Sometimes, I wonder if some of those platforms could have survived if they jumped on the Linux bandwagon and kept developing their hardware. But maybe their fate was sealed because they depended on the bundling of their proprietary OS and hardware, neither of which was able to adapt to the new order...
RetroTechie 2mo ago
You're on the right track. But imho it's about hitting a sweet spot in whatever the market wants @ a certain time. There's a lot of luck involved. x86 hit that sweet spot: 8088/8086 performance nicely between much-weaker, memory constrained 8-bitters and too-expensive SPARK/MIPS/Alpha etc workstations. Then the BIOS situation opening the door for PC clone builders, Intel's good fabbing, and presto: x86 took off. People just bought PCs because economies of scale provided increasing bang/buck compared to other offerings. ARM: grew steadily in embedded. Then "mobile" became big, ARM was objectively better than x86 there (battery! perf/W), and the market size provided huge $$ royalties that enabled ARM to hire top-talent engineers & improve their next designs. Leaving their competition in the dust. Steadily upping performance lead to things like ARM based laptops & servers. RISC-V is largely riding the "open" wave. Which does translate into practical advantages like driving down product cost, software support improving fast due to the shared ecosystem, etc. But again: much luck involved - timing of its introduction, cheap FPGA boards becoming available to developers & students, the ISA itself being fairly sane (even called "boring", which is good in this context), its modularity positioning it across a wide range of markets, coumtries like China looking for tech-independence, etc. This much like ~1850's industrialisation in Britain: ANY one of the factors missing could have lead to failure. Personally I have high expectations for RISC-V. But regardless how it'll pan out: it's well past critical mass, so it's here to stay.

jackb4040 2mo ago

It's fascinating to me what you're describing. That ISA prevalence basically comes down to the anarchy of the market, and theoretical differences in the actual design don't really factor in. Is this true? Can we analyse the reasons we expect RISC-V to have better performance, and possibly even extrapolate that to a theoretically even better ISA and skip over RISC-V entirely?

strenholme 2mo ago
Getting RISC-V to have better performance is a matter of in-chip optimizations (caches, pipelines, etc.) and high quality performance oriented fabs. The dominance of x86 after the dot-com bubble popped shows that one can get incredible performance even from an ISA which is a hack on top of a hack on top of another hack. [1] In terms of a “theoretically even better ISA”, if anyone has any proposals, I would love to see links to them. In particular, the article “RISC-V: They Should Have Known Better” does not propose an ISA (except mentioning that the author feels AArch64 is much better), so I find its criticisms dubious. [1] I will make one ISA propsal: x86_64 should have had 32 instead of 16 registers, but 16 registers at least is quite a bit better than the 4-8 registers the 386 had.
- jackb4040 2mo ago
  But is there any article / papers / field of study that explores the theoretical maximum of various architectures, given infinite resources? Do they begin to converge, such that a highly optimized Arm looks similar to a highly optimized RISC-V core? If we are near / past the point of diminishing returns for x86, how mathematically rigorous is our proof of that?
- anon-3988 2mo ago
  > [1] I will make one ISA propsal: x86_64 should have had 32 instead of 16 registers, but 16 registers at least is quite a bit better than the 4-8 registers the 386 had. Is "registers" still a real thing or its just an illusion at this point? I am pretty sure there are "virtual" registers or micro instructions (something like that, I forgot the terminology)
  - inkyoto 2mo ago
    Registers are very much real, and their number being available at the ISA level will continue to matter regardless of the actual number of shadow registers. Being able to store, e.g. 10 vs 5, local variables in a larger register file has performance implications[0] strong enough to consider larger register files an advantage. [0] The reduced number of memory-to-CPU and vice versa data transfers for transient computation results.

inkyoto 2mo ago

Competing RISC designs tanked for a number of reasons, but not just because Intel and AMD started pumping money into their products. RISC vendors were in the business of selling hi-end workstations and servers that required their own respective RISC CPU's, which meant that each vendor had its own, in-house CPU design arm and either their own fab or they outsourced the CPU manufacturing to someone else. In a way, the RISC CPU was a by-product of what they sold but never the product they sold alone. Two problems followed. The CPU design is an expensive process, and keeping one's own fabs up to date with the latest and greatest manufacturing process is even more expensive, especially as the designs and processes advanced. It eventually became prohibitively expensive to maintain one's own fab, and RISC vendors started falling behind the bleeding edge (DEC, Motorola, etc.). IBM managed to get away with it for a time, but eventually, they also divested. The second problem concerned the outsourcing of the CPU manufacturing. Those RISC vendors (e.g. SGI with their MIPS) who did not have their own fabs had to contract a fab (e.g. NEC). Such a fab would produce a diverse range of microchip products, and a CPU would be just one of them. Which typically meant not the latest and greatest process, but at least a generation behind. Whereas both Intel and AMD were dedicated CPU design and manufacturing houses (although AMD also divested their fabs later), so they could specifically focus on what mattered for CPU's and for CPU's only. That said, for Intel and AMD, the CPU was the product, whereas for the RISC vendors, it was not, however important, the CPU was for them.

TMWNN 2mo ago

>Right now, RISC-V is mainly being used in cheap embedded components. Considering that x86 and ARM also were made for cheap computing, until becoming the dominant high end processor, history tells us that the cheapest ISA is the one which will become the highest performance one. You surely mean "history tells us that the cheapest and largest-volume ISA is the one which will become the highest performance one". It's not "RISC" having reached x86 levels; it's ARM variants. They did so with volume that for the first time in modern computing massively exceeded x86's. Apple's PA Semi acquisition has resulted in wizardry, but that wizardry would not have been possible without the massive volumes TSMC enjoys. In any case, I'm not convinced that the above is sufficient; there has to be some level of technical superiority (or at least reasonably equal-level) as well. Otherwise, some inexpensive microcontroller that is manufactured at 100X the volume of x86 would have taken off. Does RISC-V have enough "goodness" in its design? I do not know.

hajile 2mo ago
Here's a good one. Qualcomm beat ARM in court and reportedly pays 2-3% royalties where ARM was demanding 5-10% royalties. Qualcomm's ARM license expires around 2028 with an option to extend to 2033 (for some amount of money). If Qualcomm is locked into ARM when renewal comes up, ARM is going to not only name the higher price, but likely charge even more to recover their lost revenue. Qualcomm is already designing their own cores and ARM is charging them billions for the privilege. Increasing net profits 2-3% for simply doing the thing you are doing seems like a very easy choice. Increasing net profits 5-10% (maybe more) after the price hike seems like a fiduciary responsibility. This isn't just talk either. Qualcomm already proposed a RISC-V Znew extension (nearly 300 pages of changes to make the ISA more like ARMv8). They bought Ventana (a company already done with their second very wide RISC-V design). They partnered with other companies to make Quintauris for promoting RISC-V too. There's a non-zero chance we see a RISC-V design from Qualcomm before 2028 and I believe a near 100% certainty of a RISC-V design before 2033.

hn_submit 2mo ago

The x86 only caught up because of process technology, less so due to technological innovation (RISCifying x86 architecture). DEC, HP and MIPS simply couldn't keep up with Intel, which had its own fabs. And this was at a time when fabs-for-hire with world-leading process technology like TSMC didn't yet exist. Today, almost any fabless manufacturer can order world-class leading semiconductors from TSMC, just like Apple is doing now. Drawback is that most RISC-V manufacturers are in China, which don't have access to TSMC's manufacturing technology. And Apple is heavily invested in ARM since it owns part of the technology.

drbscl 2mo ago

> It has been only in the 2020s that RISC processors have gotten x86_64 levels of performance, notably in the the Apple M series of processors It's worth keeping in mind that modern ARM isn't really all that _RISC_, number of instructions in these chips is starting to approach x86_64 territory pretty fast

saltcured 2mo ago

It was also a messy time where software did make a lot of difference to your experience of performance. I had a few of these apples to oranges comparisons that frustrated me, as someone who absorbed the 90s counter-culture message that MS and Intel were monopolistic and needed to be displaced. In the mid 90s, I got myself a DEC Multia (small Alpha-based workstation) to run Linux. It was fast at some things, but useless to browse the newly emerging web. Netscape Navigator wasn't available as an Alpha binary, and the emulated x86 was just as slow as an early Python based browser. Running Netscape on a 486DX3-100 was night and day like visiting the future. Some other native programs went the other way, with the Alpha beating the 486 dearly. But the web browser became more and more significant. In college, I was also told I should covet Sun hardware. At my first job, I got issued a Sun Ultra workstation of some sort. I was appalled at how slow it was for my FOSS C programming workflows with autoconf/make/gcc etc. I started bringing in a Dell notebook with a Pentium-MMX running Linux, and it ran circles around the Ultra for actual day to day tasks. On the other hand, when I had to run certain commercial tools like Purify, the Sun was useful again. I also had exposure to supercomputer centers at the time, doing portability work for our HPC codebase. It was often crazy how slow these platforms were for development work. There may have been a little bit of neglect by the vendors or IT groups in terms of what hardware they dedicated as front-end service nodes on these big machines. But, there were also dramatic differneces in the operating system behavior, tuned to get one user-level job running and get out of the way. They were terrible at multitasking, and this showed through in CLI/scripted interactivity too. Sometimes, I wonder if some of those platforms could have survived if they jumped on the Linux bandwagon and kept developing their hardware. But maybe their fate was sealed because they depended on the bundling of their proprietary OS and hardware, neither of which was able to adapt to the new order...

RetroTechie 2mo ago

You're on the right track. But imho it's about hitting a sweet spot in whatever the market wants @ a certain time. There's a lot of luck involved. x86 hit that sweet spot: 8088/8086 performance nicely between much-weaker, memory constrained 8-bitters and too-expensive SPARK/MIPS/Alpha etc workstations. Then the BIOS situation opening the door for PC clone builders, Intel's good fabbing, and presto: x86 took off. People just bought PCs because economies of scale provided increasing bang/buck compared to other offerings. ARM: grew steadily in embedded. Then "mobile" became big, ARM was objectively better than x86 there (battery! perf/W), and the market size provided huge $$ royalties that enabled ARM to hire top-talent engineers & improve their next designs. Leaving their competition in the dust. Steadily upping performance lead to things like ARM based laptops & servers. RISC-V is largely riding the "open" wave. Which does translate into practical advantages like driving down product cost, software support improving fast due to the shared ecosystem, etc. But again: much luck involved - timing of its introduction, cheap FPGA boards becoming available to developers & students, the ISA itself being fairly sane (even called "boring", which is good in this context), its modularity positioning it across a wide range of markets, coumtries like China looking for tech-independence, etc. This much like ~1850's industrialisation in Britain: ANY one of the factors missing could have lead to failure. Personally I have high expectations for RISC-V. But regardless how it'll pan out: it's well past critical mass, so it's here to stay.