Battery Life While Using External Monitor on rMBP is Less

batterydisplay

I have a Retina Macbook Pro 2014, in clamshell mode attached to a full HD monitor.

I see that battery lasts much less when connected to an external monitor. Is there any explanation to why this happens? External monitor has its own power source, and Full HD is less than retina resolution.

Is there any overhead associated the mini Display Port?

Best Answer

The reason is because when you connect an external display, even if you close the laptop and use it in clamshell mode, the laptop automatically switches from an integrated video card (this uses much less power) to a more powerful, discrete video card (this uses a lot of power).

This is also true regarding Intel Iris Graphics, which has different power profiles (see the "Power Management" section). Also read on Embedded DisplayPort (eDP), and it's possibilities in terms of saving system power and further extend battery life in portable PC systems. I'm not the specialist in GPU-chips architecture, but my guess is, that the difference is exactly in using of Embedded DisplayPort on a mobile CPU, against of DisplayPort connections when on external monitor.

So the battery is drained more on when external monitors are connected, it needs more GPU power. Monitor itself does not drain the battery, as it's connected to external power.

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MacBook – External display black on rMBP 11,1

You have a solid troubleshooting technique, so I'd agree the adapter, or the VGA cable are likely culprits. Sometimes it's as easy as the cable not sitting well in the connector, and that could mean it connects the necessary pins for detection/sync but not for actual display.

One other thing I could think of is if the monitor has a source selector, i e if it has multiple inputs for VGA/DVI etc, and the right one isn't chosen. That's probably not the case though as you say it responds to resolution change.

MacOS – rMBP – El Capitan – External monitor blurry

There's a Ruby script here:

https://gist.github.com/bastibense/6549835

#!/usr/bin/ruby
# Create display override file to force Mac OS X to use RGB mode for Display
# see http://embdev.net/topic/284710
# 
# Update 2013-06-24: added -w0 option to prevent truncated lines

require 'base64'

data=`ioreg -l -w0 -d0 -r -c AppleDisplay`

edid_hex=data.match(/IODisplayEDID.*?<([a-z0-9]+)>/i)[1]
vendorid=data.match(/DisplayVendorID.*?([0-9]+)/i)[1].to_i
productid=data.match(/DisplayProductID.*?([0-9]+)/i)[1].to_i

puts "found display: vendorid #{vendorid}, productid #{productid}, EDID:\n#{edid_hex}"

bytes=edid_hex.scan(/../).map{|x|Integer("0x#{x}")}.flatten

puts "Setting color support to RGB 4:4:4 only"
bytes[24] &= ~(0b11000)

puts "Number of extension blocks: #{bytes[126]}"
puts "removing extension block"
bytes = bytes[0..127]
bytes[126] = 0

bytes[127] = (0x100-(bytes[0..126].reduce(:+) % 256)) % 256
puts 
puts "Recalculated checksum: 0x%x" % bytes[127]
puts "new EDID:\n#{bytes.map{|b|"%02X"%b}.join}"

Dir.mkdir("DisplayVendorID-%x" % vendorid) rescue nil
f = File.open("DisplayVendorID-%x/DisplayProductID-%x" % [vendorid, productid], 'w')
f.write '<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">'
f.write "
<dict>
  <key>DisplayProductName</key>
  <string>Display with forced RGB mode (EDID override)</string>
  <key>IODisplayEDID</key>
  <data>#{Base64.encode64(bytes.pack('C*'))}</data>
  <key>DisplayVendorID</key>
  <integer>#{vendorid}</integer>
  <key>DisplayProductID</key>
  <integer>#{productid}</integer>
</dict>
</plist>"
f.close

You'll have to run it in El Capitan's rootless mode for it to work.

Best Answer

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