T29 Boost Circuitry and its importance in a Macbook Thunderbolt Failure

Computer Repairs Sydney
2 min readOct 2, 2016

Developed by Intel, Thunderbolt is the brand name of a hardware interface that allows for connection of your computer to external peripherals. Up to six different peripherals can be supported using one connector via an array of topologies. Thunderbolt combines DisplayPort and PCI Express into a singular serial signal and goes as far as providing DC power. All this is done using one cable. Both Thunderbolt 1 and 2 use similar connectors as MDP Display port whereas the Thunderbolt 3 utilizes Type-C Universal Serial Bus.

thunderbolt display port

This revolutionary I/O tech fully supports high-performance data devices and high-res displays through one compact port. Like most of Apple’s products, Thunderbolt, sets entirely new standards for speed, simplicity, and flexibility. With 10Gbps of throughput, Thunderbolt gives you two channels on one connector; making it not only ultra flexible but also ultra-fast and efficient.

How the T29 Boost Circuitry Works

For Thunderbolt to operate effectively, it requires the correct amount of power running through it. Like all the other components such as LED backlight and analog circuits, Thunderbolt requires a much more higher voltage than what the input supply voltage has to offer. This particular hardware interface needs a little extra juice to power up. Fortunately for all Macbook users, the T29 Boost Circuitry steps in to provide the required voltage for running Thunderbolt. By turning up the voltage from source supply and boosting it to around 15 Volts, the T29 Boost Circuitry is perfect for power demanding interfaces like Apple’s Thunderbolt.

If your T29 Boost circuitry or Thunderbolt itself is faulty, then some connected components might fail to work as should. This means that some of your RAID arrays, network interfaces, hard drives and video capture solutions will be off the fritz. Now, while Thunderbolt itself can deliver up to 10 watts to any connected device, the performance is limited if the power is being drawn from your Macbook’s battery. For the best performance and optimal functionality from both your computer and any Thunderbolt connected devices, anything that has its own power supply should be connected.

One of the most common problems with the T29 Boost Circuitry is that it often shorts the PPBUS_G3H to ground. This means that not enough power will be reaching the Thunderbolt ports, thus rendering it useless. Before you take your computer apart and replace dozens of ports looking for the problem, make sure you take your Macbook computer to an Apple certified repair shop for diagnosis and repairs. The problem could be as simple as malfunctioning T29 Boost Circuitry.

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