iMac Pro iMac Pro - CPU - Intel SpeedStep

[gpociej]

Hi there

I'm new user of iMac Pro and I would like to understand few things that looks unclear to me and now I'm focusing on CPU speed and Intel SpeedStep.

I own 8-core version which from what I discovered (i.a. by HwInfo on Boot Camp) should step down as low as 1200 MHz without load.

According to iStat Menus my CPU running mostly near 4 GHz even when I'm doing nothing special (Safari, Mail, looking on Finder, Spotify) and CPU load isn't beyond 5%.
When I'm literally doing nothing clock going near 3 GHz, sometimes near 2 Ghz but never reaching 1.2 Ghz even when all app are closed.
Besides that there are pretty high fluctuations in idle, clock doesn't last when there's nothing happening.
(Under Boot Camp there is no problem for reaching (and staying on) 1.2 Ghz when idling)

I would much appreciate user reports how their iMacs acts idling or working on very low load.

PS.
When I was writing that post, listening to Spotify, with Mail, Evernote and few other small apps in background my CPU was staying on ~3,9-4 GHz.

 

[294307]

My regular iMac with an i5-7500 also has Intel SpeedStep and I have never noticed it go below 2.5 GHz (it has a nominal clockspeed of 3.4 GHz). There is no issue here – it's a desktop computer and therefore does not need to downclock as aggressively as it would on a MacBook Pro.

 

[gpociej]

Thanks for reply.
Looks like iMac manages power states a bit different than Windows PC.

Would be nice if any iMac Pro user would comment how his machine is doing...

 

[elewarr]

I just checked (18-core version), with no user interaction and almost no user apps running, lowest freq. was ~1.2. It seems to idle between 1.2-2GHz on macOS 10.13.6. I'm using default settings for fans BTW.

 

[SecuritySteve]

Confirmed what @elewarr said on the 18 core version. My clock goes to around 2 GHz (base core frequency) while idling. The moment anything happens though I get 4-4.3GHz. I think this may be to save on thermal dissipation. Running at a lower frequency while idle produces less heat, which helps in an AIO form factor.

Seeing as I never would have noticed this, had I not been looking, I think this is actually a rather neat and well-done feature. It saves you on your power bill, and your performance.