3 ms·
Well, the meaning of "reduced" has shifted from "not having specialized instructions" to "load-store and preferably fixed-length". Here's a CRC32 impl using PO
by floatboth 7y ago
Well, the meaning of "reduced" has shifted from "not having specialized instructions" to "load-store and preferably fixed-length".
Here's a CRC32 impl using POWER8/9 polynomial instructions: https://github.com/antonblanchard/crc32-vpmsum https://github.com/antonblanchard/crc32-vpmsum — coincidentally, you don't have to do this on ARM, ARM just has CRC32 instructions.
> hardware-level decimal-floats (for those bankers running COBOL)
IBM being IBM :) I've heard somewhere that they are sharing some internals between POWER and z/Architecture (mainframe) chips. No idea how true it is and how much is shared if true, but a scenario like "decimal floats were implemented because mainframes are using the same backend with a different frontend, so we exposed them in the POWER frontend too" sounds quite plausible.
- monocasa 7y agoIBM likes decimal floats because of COBOL (and maybe RPG?). To be fair, even back in the day decimal arthimetic could at least have an argument made for it on RISC chips. https://yarchive.net/comp/bcd_instructions.html https://yarchive.net/comp/bcd_instructions.html
- CalChris 7y agoWell, the meaning of "reduced" has shifted from "not having specialized instructions" to "load-store and preferably fixed-length". Ain't that the truth. Reduced never meant anything; they never defined it. Patterson said they cooked up the name on the way to a grant presentation. I think they should call it Warmed Over Cray. What was new in RISC that wasn't in Cray? It was like the Geometry Engine; it was possible for an academic department to accomplish but that doesn't mean they accomplished anything that hadn't already been done. preferably fixed-length Or fixed-length/2.