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Keeping POWER relevant in the open source world

peter.czanik.hu

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Re: Keeping POWER relevant in the open source world

#41

Post by classichasclass »

markphip wrote: post #29

The most compelling argument for POWER was to make sure there is competition to amd64/x86 and we do not develop a monoculture. I think arm and risc-v have filled that hole nicely and taken over for POWER. Without readily available and affordable hardware I do not see much of a future for POWER in open-source. It seems entirely dependent on IBM to keep it going unless this changes.

I'm not sure I agree about RISC-V. ARM is now indisputably in the same performance ballpark as x86_64 (M1 most obviously but there are others), as is Power, but RISC-V has a ways to go before it can compete on the same turf. It hasn't even really competed with ARM in embedded, despite its advantages there (though it has all but killed the zombie corpse of neo-MIPS).

I do agree that without other processor makers, however, the Power ecosystem is crucially overdependent on IBM policy. This is not a new problem but it hasn't gotten any better with OpenPOWER.

Re: Keeping POWER relevant in the open source world

#42

Post by classichasclass »

chasil wrote: post #27
sidpatil wrote: post #9

Earlier quoted context omitted.

PowerPC is a derivative of the original POWER architecture by IBM. https://en.m.wikipedia.org/wiki/IBM_POWER_instruction_set_ar...

Also used in the Xbox 360, and an exotic variant was also in the PlayStation 3.

And GameCube, and Wii/Wii U.

Re: Keeping POWER relevant in the open source world

#43

Post by AlbertoGP »

classichasclass wrote: post #40
AlbertoGP wrote: post #37

Earlier quoted context omitted.

My main workstation is too a Raptor Power9 running Void since November 2019, and I’m very happy with it although as the article mentions, “My experience with firmware is that open source does not mean necessarily better, rather the opposite”. OpenBMC (the firmware for the little ARM-based embedded computer that boots the big one) has a number of rough edges. From time to time I submit patches to software to make it w…

Interesting, never heard about them asking about ISA changes. Where was that done? There are some lovely new instructions in Power10 but until they get the firmware source out fully I won't use them in the Firefox JIT.

It was through the IRC channel. I sent a direct message as response and exchanged a couple of sentences, then they gave me their IBM email address to submit the detailed proposal. My understanding was that it would have to be justified and for that I would have to show that it could be more efficient than an implementation based on the existing SIMD instructions which I’m not familiar with. I suspect that the kind of instructions that could actually be put there might not perform better than that.

I regret not sending at least an amateurish proposal, I still think it would be a good idea to have no-cost UTF-8 en-/decoding. Not just for text, but for general variable-length encoding of other kinds of data.

Re: Keeping POWER relevant in the open source world

#44

Post by classichasclass »

goodpoint wrote: post #3

IBM had the opportunity of being the royalty-free ISA that RISC-V is. Or even release the cores "IP". They squandered it.

The ISA is open and royalty free.

There are at least three open cores, all IBM funded or designed:

https://github.com/antonblanchard/microwatt https://github.com/openpower-cores/a2o https://github.com/openpower-cores/a2i

The last two are older but they work. Microwatt is developing by leaps and bounds.

Re: Keeping POWER relevant in the open source world

#45

Post by classichasclass »

AlbertoGP wrote: post #43
classichasclass wrote: post #40

Earlier quoted context omitted.

Interesting, never heard about them asking about ISA changes. Where was that done? There are some lovely new instructions in Power10 but until they get the firmware source out fully I won't use them in the Firefox JIT.

It was through the IRC channel. I sent a direct message as response and exchanged a couple of sentences, then they gave me their IBM email address to submit the detailed proposal. My understanding was that it would have to be justified and for that I would have to show that it could be more efficient than an implementation based on the existing SIMD instructions which I’m not familiar with. I suspect that the kind of…

Very interesting. Which channel specifically?

VSX is really where the new development is happening, but it's become quite complete. The PC-direct instructions first made available in P9 also really closed a gap (beforehand you had to do bl with a weird flag to get PC in LR without trashing the history table).

Re: Keeping POWER relevant in the open source world

#46

Post by IainIreland »

DannyBee wrote: post #38
ballen wrote: post #7

Earlier quoted context omitted.

The IBM XL compilers have had a free to download community version for a little while now [1]. They also appear to be adopting LLVM [2]. 1. https://www.ibm.com/products/xl-cpp-linux-compiler-power 2. https://community.ibm.com/community/user/power/blogs/si-yuan...

In some ways, #2 is sad to me. Don't get me wrong, I have worked a ton on LLVM and love it. But at least when i was there, IBM's interprocedural middle-end (TPO) was some of the nicest and well structured C++ compiler code i had seen in a long time. It was well written, well commented, and well architected.

It may have changed since I left, but my understanding as of a few years ago was that IBM was replacing the front-end with Clang but continuing to use TPO (at least for now).

Re: Keeping POWER relevant in the open source world

#47

Post by AlbertoGP »

classichasclass wrote: post #45
AlbertoGP wrote: post #43

Earlier quoted context omitted.

It was through the IRC channel. I sent a direct message as response and exchanged a couple of sentences, then they gave me their IBM email address to submit the detailed proposal. My understanding was that it would have to be justified and for that I would have to show that it could be more efficient than an implementation based on the existing SIMD instructions which I’m not familiar with. I suspect that the kind of…

Very interesting. Which channel specifically? VSX is really where the new development is happening, but it's become quite complete. The PC-direct instructions first made available in P9 also really closed a gap (beforehand you had to do bl with a weird flag to get PC in LR without trashing the history table).

The IRC channel was #talos-workstation on FreeNet, now on Libera.Chat.

Do you know of some minimal example of calling VSX instructions from C?

Ideally just one .c file and one Makefile or README with the exact GCC command to compile it, plus a pointer to documentation describing each instruction. I’ve seen assembler inserted into C source code with GCC, but I’ve never done it and I assume there are some non-obvious details to take into account.

Re: Keeping POWER relevant in the open source world

#48

Post by goodpoint »

classichasclass wrote: post #44
goodpoint wrote: post #3

IBM had the opportunity of being the royalty-free ISA that RISC-V is. Or even release the cores "IP". They squandered it.

The ISA is open and royalty free. There are at least three open cores, all IBM funded or designed: https://github.com/antonblanchard/microwatt https://github.com/openpower-cores/a2o https://github.com/openpower-cores/a2i The last two are older but they work. Microwatt is developing by leaps and bounds.

I'm aware. The problem is that the ecosystem has been opened up too late, while the RISC-V ship has sailed and also missing the opportunity to disrupt datacenters and phones.

Re: Keeping POWER relevant in the open source world

#50

Post by chasil »

DannyBee wrote: post #28

IBM has had this argument internally for eons. When i was there, two decades ago , people were making presentations internally saying the same thing - "without affordable volume machines that random people can buy and use to develop, this ecosystem will fail" Then, like now, there were even organizations/companies people thought might eventually take care of doing this that weren't IBM (Spoiler alert: They didn't) Gi…

This is starting to feel a lot like the DEC Alpha, at least from the perspective of the 3rd party motherboards.

The ubiquity of x86 and ARM does not leave much room for the Power architecture in the general market.

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