Published November 9, 2024

This article documents the internal storage upgrade of a base-model M4 Mac mini, unboxed the day after the model's release. The goal was to increase internal storage from 256 GB to 2 TB. The author reports that the upgrade reached 1 TB. Memory on Apple silicon systems cannot be upgraded, according to the author's findings.

Specifications and Ports

The test unit was the base model, with the following configuration:

The rear panel includes an Ethernet port, an HDMI port, and three USB-C ports that support Thunderbolt 4. The front panel includes two USB-C ports that do not support Thunderbolt, a power LED, and a headphone jack. The power button is on the underside. The power supply is internal.

Baseline Benchmarks

Benchmarks were run before disassembly.

• Geekbench 6 (CPU): Single-core score of 3855 and multi-core score of 15,515. The reported clock speed is 4.41 GHz.
• AJA System Test (storage, 4 GB file size): Approximately 1,700 MB/s for both read and write.

Teardown

Exterior and Chassis

1. Bottom panel: The plastic cover is held by four push pins and adhesive. It was removed with a spudger.
2. Bottom cover: Four T5 screws along the sides secure the cover. Four additional T5 screws hold the metal shield over the ribbon cable.
3. Fan: The fan is secured by smaller screws, identified as T3 or T4.
4. Storage modules: Storage is on removable NAND modules, similar to those in the Mac Studio. One NAND chip sits on the rear of the board and one on the front. The Mac Studio module contains four NAND chips. A T8 screw secures the module.
5. Connector panel: Four screws secure the panel. Disconnecting it provided access to the Wi-Fi board.

Wireless and Power Components

• The Wi-Fi chip is on a small board that connects to the system through a single connector.
• Three Wi-Fi antennas are integrated into the metal panel.
• The SMC clock battery is located near the Wi-Fi board.

Logic Board and System-on-Chip

• The front ports were removed. The logic board can be rotated out of the chassis after the ports are pushed back.
• The power supply is at the top of the chassis.
• The logic board is small.
• Copper foil insulating tape covers the rear of the board. Removing the black plastic insulator damaged the tape. The author states that the tape may not be reusable.
• The heat sink is secured by mounts, which were removed.

The M4 system-on-chip is similar in design to the M1 chip. Its footprint is considerably larger. Its width is about the same as the M1, but it is taller. The RAM chips are also taller than those on the M1. The heat spreader is flat, while the M1 spreader has a beveled edge.

The author replaced the thermal paste on the processor. The thermal paste on the RAM chips was not replaced, because it is a thicker compound that liquid thermal paste cannot substitute.

Storage Module Preparation

Two blank 1 TB NAND chips, model K6B2, were used for the upgrade. The author believes these chips are compatible with the M4 Mac mini. The same model has been used in the M3 MacBook Air and the iPhone 14, 15, and 16.

The NAND chips installed in the module must be blank. The author's earlier video on the Mac Studio upgrade describes the same process in more detail.

Removing the Original NAND Chips

The original chips are secured with underfill, an adhesive compound. The removal process was as follows:

1. Apply low heat to soften the underfill around the edges of the chip, especially along the top edge. Scrape the underfill away. This prevents components from lifting during chip removal.
2. Set the hot air station to 280–300 °C.
3. Lower the temperature to 270 °C when the chip begins to lift. Remove the chip.
4. Scrape residual underfill from the pads with a removal tool.
5. Apply flux and remove residual solder with a soldering iron.
6. Remove remaining solder with solder wick.
7. Clean the pads with rubbing alcohol and a paper towel.

The same process was repeated for the chip on the opposite side of the board.

Reballing the New NAND Chips

The new chips were reballed one at a time, because the stencil had warped in previous use. The process was as follows:

1. Secure the chip to the stencil in the correct position with capped tape. Align the chip with the stencil holes.
2. Apply solder paste, which consists of small solder balls suspended in flux, into the stencil holes. Press the paste in several times to ensure even deposits.
3. Set the hot air station to 280–300 °C. Heat the paste until it melts onto the pads. Hold the stencil flat against the chip with tweezers.
4. Remove the chip from the stencil.
5. Apply additional flux. Heat the chip to seat the balls fully into the pads.

The second chip was reballed with the same process.

Soldering the Chips to the Module

1. Heat the board to bring it to a suitable temperature.
2. Apply a small amount of flux to the pads.
3. Align the chip with the pads. Pin 1 faces the connector on both sides of the board.
4. Heat the chip with the hot air station to solder it to the board.
5. Allow the board to cool. Flip the board and solder the second chip to the opposite side.

Restore and Verification

The author did not replace the shield under the ribbon cable before testing. The power button was reconnected to power the device for testing.

Restore Attempts

1. The Mac mini was connected to an M1 MacBook Air through a USB-C port. The author selected the port furthest from the HDMI port. The device was placed into DFU mode by holding the power button while connecting power. The front LED flashed amber, confirming DFU mode.
2. Holding the Option key while selecting Restore Mac in Finder, the author selected the IPSW file for the M4 Mac mini. The restore did not proceed. The author attributes the failure to the MacBook Air running macOS Sonoma. The restore of this newer model requires macOS Sequoia.
3. An M1 Mac mini running macOS Sequoia was used for the restore. The restore began. The DFU port that worked was the center port. The author states that all three rear USB-C ports enter DFU mode, but only the center port worked in this test.

Restore with 1 TB NAND Chips

The first restore attempt with the two 1 TB NAND chips did not succeed after repeated attempts. The author believes one or both chips were defective. No spare 1 TB chips were available.

The process was repeated with two 512 GB NAND chips. The resulting configuration is 1 TB. The restore completed successfully. The display showed no video during early stages of the restore, which the author states may be normal for the M4 Mac mini. The display later produced video. The system booted after the restore.

Post-Upgrade Verification

• About This Mac: Confirmed the same machine with the upgraded storage.
• System Profiler: Detected an Apple SSD AP1024Z, confirming 1 TB of internal storage.

The upgrade produced 1 TB, not the 2 TB target.

Post-Upgrade Benchmarks

• Geekbench 6 (CPU): The multi-core score was 14,633. The author recalls the original multi-core score as approximately 15,000. The original result was not saved. The author attributes the difference to variance in the test.
• AJA System Test (4 GB file, continuous mode): The author reports approximately 3 Gb/s for write and 2 Gb/s for read. The read and write speeds were both about 1,700 MB/s before the upgrade. The author describes the result as slightly better than expected and sufficient for general use.

Cost and Component Sourcing

• The two 1 TB NAND chips cost approximately $160 for the pair.
• The two 512 GB NAND chips used for the successful upgrade cost approximately $90 for the pair.
• The author ordered four NAND chips. The supplier shipped three. The author did not have the fourth chip required to complete the 2 TB configuration.

Summary

The upgrade produced a 1 TB internal storage configuration on the M4 Mac mini, from the base 256 GB model. The 2 TB target was not reached. The author attributes the failure to the first set of 1 TB NAND chips and to the missing fourth chip in the order. The total upgrade was completed within a few hours of receiving the unit.