News for hackers. Stuff that matters.

A comment on 64-bit RISC-V core claims 10x better CoreMarks/Watt compared to other 3-5GHz CPU.

Re:64-bit RISC-V core claims 10x better CoreMarks/Watt compa... by gchadwick on Thursday December 03, 2020 @05:46AM (#25287643)
The claims here do seem a little suspicious, for one CoreMark is not the be all and end all of benchmarks, especially if you're trying to compare yourself against the M1 and other CPUs in a similar class. You need a far broader base of benchmarks for a decent comparison (for one thing CoreMark won't give the memory system much of a workout).

A big red flag is the Cortex-A9 comparison that is used, being described as the faster arm processor for CoreMark, if you go to to EEMBC's CoreMark score database (https://www.eembc.org/coremark/scores.php), search 'arm' a Cortex A9 part does indeed take top score. Note this are just user sumbitted scores without any real curation, searching 'arm' isn't guaranteed to give you all arm cores in the database, plus results could have errors in.

Given the age of the core (it was introduced in 2007) I'd be rather surprised if the A9 was the best performing arm core on CoreMark. Though From a quick google I can't find CoreMark numbers for other arm A-class cores.

[ Parent | on HN ]
Re:64-bit RISC-V core claims 10x better CoreMarks/Watt compa... by BlueToth on Thursday December 03, 2020 @08:06AM (#25288422)
Their math is incorrect. The M1 scores about 300K in Coremarks and has 8 cores => 37.500 per core. M1 consumes about 12W => 1.5 W/core and thus: 37.500 ÷ 1.5 W/core = 25 K Coremarks per Watt. But this company (or Andy Huang) is claiming M1 has 100 Coremarks per Watt! Why don’t people check their math if it sounds far off?
[ Parent | on HN ]
Re:64-bit RISC-V core claims 10x better CoreMarks/Watt compa... by imtringued on Thursday December 03, 2020 @08:46AM (#25288752)
I saw multiple people (outside of HN) come up with similar numbers for the M1. The numbers are impressive (2x-3x more efficient than M1) but the extreme dishonesty makes the design look like snakeoil. If you're ahead why lie? Probably because the design isn't actually as good as the press release implies.
[ Parent | on HN ]
Re:64-bit RISC-V core claims 10x better CoreMarks/Watt compa... by ddeck on Thursday December 03, 2020 @08:24AM (#25288554)
The photo from the press release doesn't inspire much confidence.

It seems that their measurements are based on what the current reading said on the screen of a $60 noname ("Hanmatek") power supply. [1]

I don't now much about CPU loads, maybe it's constant and the reading is reasonably accurate, but I'd at least hope for some better measuring equipment.

[1] https://www.amazon.com/Adjustable-HANMATEK-HM305-Variable-Sw...

[ Parent | on HN ]
Re:64-bit RISC-V core claims 10x better CoreMarks/Watt compa... by jonplackett on Thursday December 03, 2020 @06:18AM (#25287800)
It seems to be orders of magnitude more efficient though.

Is the focus on efficiency covering up that it can't scale up to be actually as fast as the m1?

It all seems a bit too good to be true, what's the catch?

[ Parent | on HN ]
Re:64-bit RISC-V core claims 10x better CoreMarks/Watt compa... by toasted_flakes on Thursday December 03, 2020 @07:26AM (#25288193)
See this comment[0] from a previous submission, but long story shorts, the numbers are literally made up.

[0] https://news.ycombinator.com/item?id=25263011

[ Parent | on HN ]
Re:64-bit RISC-V core claims 10x better CoreMarks/Watt compa... by gchadwick on Thursday December 03, 2020 @07:48AM (#25288326)
> It all seems a bit too good to be true, what's the catch?

Take a look at their press release here: http://www.micromagic.com/news/CoreMark_PressRelease.pdf

They claim 11'000 CoreMarks at 4.25 GHz in what is presumably their more efficient running mode (0.8v, consuming 200 mW). That gives you 2.58 CoreMark/MHz which is quite poor even comparing against high-performance embedded, let alone the likes of the M1 (The arm M4 can achieve 3.42 CoreMark/MHz for instance). That indicates a microarchitecture that will choke on more complex workloads.

I think what they've done is produce a super simple 64-bit RISC-V core they've focused on clocking as fast as possible and pushing the power down as much as possible. Does a good job on CoreMark/Watt numbers (assuming they're even correct!) but useless for any real application.

Either you want a desktop/server style workload in which case their IPC, and hence total performance and efficiency, will drop through the floor, or you have something more CoreMark style in which case you don't need it running at anything like 5 GHz and you're far better off with one of the many embedded cores on the market.

[ Parent | on HN ]