undefined | Better HN

0 pointslhl5y ago0 comments

> Those SoCs hit (and sustain) their top clocks, whatever those are for that specific SKU.

This is actually completely wrong. Almost no laptops sustain their top (boost) clock on heavy workloads. Most usually only sustain max performance for minutes (or seconds!) before throttling. Here's an example chart that shows how various premium Athena/Evo U laptops perform: https://www.notebookcheck.net/Asus-Zenbook-S-UX393JA-Laptop-...

On the workstation side, people complain about Macbooks, but recent MBPs actually throttle their Intel H processors less than a comparable XPS 15 for example: https://www.notebookcheck.net/Apple-MacBook-Pro-15-2019-in-r...

If you are interested in how modern Intel laptop chips throttle and what base and boost clocks mean, you want to do a search for PL1, PL2, and Tau. For AMD chips, you will want to look up STAPM, Fast and Slow PPT.

Note that while a i7-10875H's top "boost" clock is 5.1GHz, the sustained "base" clock is only 2.3GHz. This is so low to be meaningless as a top speed. In practice, unless your laptop's cooling is absolutely terrible, you'll probably end up mostly running in the 3-3.5GHz range under full load. In comparison, on a properly cooled desktop system, a same-gen i9-10900K desktop system should be able to maintain a sustained (all-the-time) clock of about 5GHz (very close to its 5.3GHz boost). AMD chips scale a little bit better due to 7nm having better power efficiency and how PPT works, but the same ratio roughly applies.

0 comments

xondono5y ago

I’ve actually worked with Ryzen SoCs myself (I do board design).

This is the problem with all the marketing BS. When I talked about “top clocks”, I wasn’t referring about “boost” clocks. I’m talking of the clocks that the SoC is designed for (that won’t appear on the box), i.e. a lot of laptops are not leaving “performance gaps” due to bad cooling, those SoCs are designed for that level of performance and attaching a fat copper heatsink won’t do much difference.

I had a lot of trouble with a client that complained that our board was not properly designed because the performance they were seeing was not “as advertised”. In the end we had to ship the whole thing to AMD, and have them test the system with a thermal sink. Everything was as expected.

If anyone is interested in this kind of stuff, your explanation is really good, so I won’t add anything because I’d probably do a terrible job :)

lhlOP5y ago

I agree that there's a lot of misunderstanding on clocks - I've been on the other end - evaluation and validation of embedded boards, including V1000 Ryzen SoCs, but I think I'd disagree somewhat with the characterization of clocks as purely "marketing BS."

Back in the day, most CPUs had had a fixed clock, but these days modern Intel and AMD chips simply don't - they all clock opportunistically, which depends on powers, thermals, but also workload (try running an AVX-512 loads for example). How do you characterize "clock" in this context? Base (minimum) and Boost (hard limit, now split to Max Turbo <2C and All Boost MC) seem to be reasonably sensible numbers.

Now we can argue semantics all day, but to bring it back around if you're just going to say "top clocks" is what the SoC was designed for at a specific workload/power envelope (In AMD's PB, that'd be PPT, TDC, and EDC) then every laptops will "hit their top clocks with no issues," but I'd say that argument (statement?) is a bit circular/pointless. ;P

j / k navigate · click thread line to collapse