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I'm sure NASA has an enormous amount of hard-earned in-house expertise in rad-hardened electronics, hard real-time safety critical software, and related things.
by jabl 4y ago
I'm sure NASA has an enormous amount of hard-earned in-house expertise in rad-hardened electronics, hard real-time safety critical software, and related things. But how much of that knowledge is tied specifically to the POWER ISA? Not much, would be my guess.
I've been following POWER at a distance, and while I'm sure the ISA itself is good enough, I'm not really convinced about the vitality of the ecosystem. The only place where serious money is being invested is in the high-end CPU's which IBM keeps developing enough to prevent their high-end captive customers from defecting. But at the lower end and embedded, it's crickets. Beyond some token efforts like the microwatt for FPGA's and an old supercomputer core design they open sourced, the whole OpenPOWER effort seems to be little more than a couple of guys producing the occasional powerpoint and press releases.
- HereIGoAgain 4y agoDepressing.
- ncmncm 4y agoCompilers have had many years of work put into generating optimal instruction sequences for POWER. That is all flushed away moving to RISC-V. Momentary "vitality of the ecosystem" just seems like a poor basis to choose the underpinnings for decades of future work. But we seem to do that every time.
- jabl 4y ago> Compilers have had many years of work put into generating optimal instruction sequences for POWER. That is all flushed away moving to RISC-V. Well, to an extent. If one looks at GCC at least (presumably LLVM as well, although I don't follow it as much), POWER-specific patches seem to amount to enabling and optimizing the latest POWER server CPU's. I can't offhand actually recall much if any work on other POWER CPU's. So all that work won't really benefit an embedded POWER core. And further, which core would that be? I haven't seen anything new in the embedded POWER market for a very long time, but maybe I'm missing something? You're certainly not going to put a POWER10 on a space probe and call it a day. So if NASA was really wedded to POWER, would they have to foot the bill to develop a new POWER core, and maintain the compiler backend for that one? Sounds a lot more expensive than picking an existing core developed by someone else, and compiler backend maintenance done by someone else as well, and rad-hardening it. > Momentary "vitality of the ecosystem" just seems like a poor basis to choose the underpinnings for decades of future work. Well, AFAICS it's not momentary but terminal decline. Now of course it might be that RISC-V dies away as well after the current excitement, but at least to me that looks much less likely than POWER reversing its fortunes in the embedded market. As to why not ARM then, I'm not sure. Might have to do with such government contracts requiring working with US companies, and both Microchip and SiFive are US, whereas ARM is British/Japanese? > But we seem to do that every time. Sure. I do think that if IBM had done the OpenPOWER thing 15 years ago and put serious money behind it, POWER could have been a worthy competitor to ARM in the embedded market, and RISC-V might never have seen the light of day. But, they didn't, and here we are.
- inamberclad 4y agoMost compiler profiles for space barely optimize anyway. Determinism is much more important than performance.