The 2011 15”/17” MacBook Pro has two graphics processors (GPU). A discrete GPU and an integrated GPU. The discrete GPU provides substantial graphics performance but uses more energy. The integrated GPU optimizes battery life by using less energy. However, many early and late–2011 MacBook Pro owners with discrete graphics cards reported that this GPU causes graphic failures and system crashes on their machines. Disabling the dedicated GPU seems to be the best fix for this issue. The process is available on GitHub for any user and it’s quite simple to do. But with each system update or PRAM reset, you will have to repeat the process all over again. Luckily, a member of the MacRumors forum – dosdude1 has found a way to PERMANENTLY disable the dedicated/discrete GPU on the 2011 15″/17″ MacBook Pro via a process called gMux IC Bypass. Let’s check it out!
What is a gMux IC and How Does It work
For beginners, the MacBook Pro notebooks utilize dynamic GPU switching between the discrete and integrated graphic cards via an IC known as the gMux chip. Basically, it is a pre-installed microcontroller, programmed with special firmware for fast GPU switching in MacBook Pro systems. This IC has 3 sets of LVDS lines connecting to it. The LVDS output lines from the dedicated GPU, the LVDS output lines from the integrated GPU, and the LVDS lines connecting to the connector for the display. When the IC received a specific command from the system, it will route the correct set of LVDS lines to the display’s LVDS output on the logic board in order to quickly switch between the GPUs.
Permanently Disable the dedicated GPU with gMux IC Bypass
So in order to permanently keep the dedicated/discrete GPU disabled, you will have to bypass the gMux IC mechanic and hard-wire the LVDS output lines from the integrated GPU straight to the lines connecting to the display. Here is the step-by-step guide to do so:
Step 0: Preparation
This modification requires precision soldering equipment, so it’s recommended to use a microscope in the process.
You also need to download the schematic for your MacBook Pro board in order to get the exact results.
After downloading these files, you can easily open and view them via specialized software like Boardviewer or Openboardview.
Step 1: Connect the Corresponding Data Lines
To begin, here is the main premise of this mod.
In these images, you can see how the LVDS data lines appear for the integrated GPU output, dedicated GPU output, and the LVDS output for the display (EG for discrete GPU, IG for integrated GPU, and CONN for connector). You can see how this data line corresponds with each set of LVDS lines. There are 12 total LVDS lines divided into 6 pairs.
In order to do this modification, you will need to connect each LVDS data line from the LVDS_IG side to its corresponding data line on the LVDS_CONN side. Here is a wiring diagram to help you solder all the data lines easily:
Step 2: Route The Clock Lines
Let’s take a look at the schematic. You will notice that there is only one set of clock lines on the LVDS_IG side (LVDS_IG_A_CLK) but 2 sets on the LVDS_CONN side (LVDS_CONN_A_CLK and LVDS_CONN_B_CLK). So what you need to do is connect the A_CLK pair from the IG side to the A_CLK resistor pair on the CONN side. After that, connect the A_CLK pair to the B_CLK pair on the CONN side.
Next, you will need to pull the LVDS_DDC_SEL_IG rail high. Doing this will route the necessary LVDS DDC clock lines to the integrated graphics card. What you need to do is connect the high side of this rail’s pulldown resistor (R6982) to the PP3V3_S0 rail. Dosdude1 recommended connecting it to a capacitor near the backlight IC (C9711), as it was the easiest and closest source of PP3V3_S0 to that point of the board.
Step 3: Enable Rails for the LCD backlight and LCD Panel power
The next things on the list is to enable rails for the LCD backlight and LCD panel power. To do so, you simply need to bridge the rails between LCD_PWR_EN, LVDS_IG_PANEL_PWR, and LCD_BKLT_EN.
Step 4: Wire the Backlight PWM signal
The last wire will be used to wire the backlight PWM signal. The purpose of this signal is to control the backlight brightness level. By default, the PWM signal is generated by the gMux IC. But with this modification, the gMux IC is no longer be able to provide this signal. As such, we will simply be wiring this rail to the LVDS_IG_BKL_ON rail. Unfortunately, it means that you won’t be able to control the backlight from the OS later. Instead, the backlight will remain at a fixed brightness.
Step 5: Cut The Power To The Discrete GPU
The last step is to cut the power to the discrete GPU after you complete all the wiring. Otherwise, it will simply produce waste heat. To do this, you will have to remove the resistor that supplies power to the GPU VCORE regulator IC, R8911.
Once you completed all the wiring processes, the system should be good to go. The final board should look something like this:
Other Method To Permanently Disable the Dedicated GPU on 2011 15″/17″ MacBook Pro
Dosdude1 also provided another method to do disable the discrete graphic card: re-programming the gMux IC with custom firmware to disable the GPU switching functionality. For more information about this method, you can check out his Youtube video here.
And that’s how to Permanently Disable the Dedicated GPU on the 2011 15″/17″ MacBook Pro. This method is still the best solution for rectifying the defective AMD GPU issue on these machines. Now you will have a fully working 2011 15″ or 17″ MacBook Pro, running off ONLY integrated GPU! No OS X modifications are necessary, and it is not reliant on any NVRAM variable. The only issues are the lack of brightness control and the external display port won’t be able to work.
