Running 2 external displays drags down MBP15 battery

fhturner

macrumors 6502a
Original poster
Nov 7, 2007
593
371
Birmingham, AL & Atlanta, GA
Wondering if others have experienced this... When I run my MacBook Pro 15" Late 2013 w/ the built-in display + iMac 27" TDM (2560x1440) + Apple Cinema Display 23" (1920x1200), the machine eventually works hard enough, runs hot enough, and blasts the fans full enough that the battery level actually DRAINS while it is plugged in. So, presumably, after a long enough session like this, the MacBook would simply run out of sufficient power and shut down. Although this admittedly isn't a common scenario, it does seem like a bit of an "Oops...oh well, f*ck it" in design/testing.

Anybody else observe this phenomenon? Suggestions for making this work more efficiently? iStat shows the GPU is clearly running hottest and obviously causing the fans to ramp up to full speed. The 2 external displays' total add'l pixels (~6 million) equate to an increase of approximately 115% over the built-in Retina panel alone...still a good bit below what a single 4K display would add (~8.3 million pixels)...

Thx,
Fred
[doublepost=1522293404][/doublepost]Interesting comparison: just removed my Late 2013 MBP15 from the aforementioned arrangement and inserted my secondary Mid 2015 MBP15 w/ only Intel Graphics in its place. The 2015 has less "stuff" running, so it has a little bit greater percentage Idle in Activity Monitor, but the fans have barely come off their idle speed of 2000rpm (one is at 2K, the other at 2200rpm). As you'd assume, the battery stays at 100%.
 

MacDawg

macrumors Core
Mar 20, 2004
19,824
4,507
"Between the Hedges"
I run a 23" Apple Cinema Display and a 27" Apple Thunderbolt Display along with my late 2013 15" MBP
Never see a drain on battery

And I keep 2 VMs open all the time (VMware Fusion)
 

fhturner

macrumors 6502a
Original poster
Nov 7, 2007
593
371
Birmingham, AL & Atlanta, GA
I run a 23" Apple Cinema Display and a 27" Apple Thunderbolt Display along with my late 2013 15" MBP
Never see a drain on battery
Hmmm...interesting. Just to clarify:

1. Is your machine "dual graphics" (with GT750) or Intel-only graphics?
2. You are using both of those displays AND the internal display at the same time?

Thx,
Fred
 

leman

macrumors G4
Oct 14, 2008
11,008
5,510
Mac laptops with dual GPUs automatically switch to higher-power GPU when connected to external display. What you are describing should not be happening though. My guess is that there is a bug/configuration problem/other issue that causes the GPU to use too much power.

Overall, it can happen that an older MBP looses charge even while plugged in, since maximal power draw of its components can exceed what the power adapter can maximally provide. However, this would only happen under very limited circumstances, when both the GPU and CPU are pushed to their limits. Your situation is clearly not normal.
 

fhturner

macrumors 6502a
Original poster
Nov 7, 2007
593
371
Birmingham, AL & Atlanta, GA
Do you by any chance have a power adapter from a 13" model?
No, it's for 15". It is, however, a MagSafe 1 w/ a MagSafe 2 adapter on it at this particular desk. But still the same 85W as MagSafe 1. For grins, I'll try it w/ MS2 next time.

Possibly, although I'm pretty sure I first noticed the high fan RPM and noise when still on ElCap at this desk setup (w/ the 27" + 23" + built-in). Interesting reading though...I might try the Nvidia web drivers for comparison. Also, when I posted this, I'm sure I was on HS 10.13.3, since 10.13.4 wasn't out for a couple more days. I will observe again, probably this afternoon when I'm back there, and see how it goes.

Thx,
Fred

P.S. Just noticed that Activity Monitor has a GPU History window now! When did that show up??
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.