Crucial CT4G3S1339M 4GB DDR3 1333MHz Mac Memory

Name: Crucial CT4G3S1339M 4GB DDR3 1333MHz Mac Memory
Brand: Crucial
SKU: CT4G3S1339M

Overview

The Crucial CT4G3S1339M is a 4GB DDR3 SO-DIMM module running at 1333MHz (PC3-10600) with CL9 timing, built specifically for Mac systems. Those specifications matter in context: DDR3-1333 CL9 is the baseline performance tier Apple used in mid-generation MacBook Pro, iMac, and Mac mini models, and Crucial's modules are tested to meet or exceed Apple's own quality thresholds — not just generic JEDEC compliance. The 204-pin SO-DIMM form factor is the laptop-derived format used in all DDR3-era Macs, and running at 1.35V (DDR3L compatible) ensures it operates within Apple's EFI power envelope without triggering memory errors.

This module is aimed squarely at users extending the productive life of a DDR3-era Mac. Whether the goal is restoring a Mac that suffered a failed stick or upgrading from a factory 2GB configuration, this module eliminates the trial-and-error risk of sourcing generic DDR3 SO-DIMMs. Crucial's compatibility verification process cross-references the module against a database of Apple hardware, making it a straightforward recommendation for anyone who wants one correct purchase rather than a string of returns. For maximum throughput, installing a matched pair in dual-channel configuration will noticeably reduce memory latency versus a single-channel setup of the same total capacity.

Key Features

Increases system performance

Compatible with select Mac systems

All memory stick modules extensively tested at the component and function level

Meets or exceeds, Apple's quality standards and requirements

Easy installation

Specifications

RAM Capacity

4GB

RAM Type

DDR3

RAM Speed

1333MHz

Compatibility

Select Mac systems

Brand

Crucial

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Pros & Cons

👍 Pros

Validated against Apple's own quality standards, eliminating the compatibility risk common with generic DDR3 modules
SO-DIMM form factor and 1.35V/1.5V compatibility covers a wide range of DDR3-era Mac configurations
CL9 latency at 1333MHz matches Apple's factory specification, ensuring no BIOS or EFI negotiation issues on installation
Each module undergoes component-level and functional testing, reducing DOA rates versus unbranded alternatives
Enables dual-channel configuration when paired with a second identical module, doubling effective memory bandwidth

👎 Cons

DDR3 1333MHz is a legacy standard — maximum per-module capacity of 4GB limits the ceiling of any DDR3-era Mac upgrade
CL9 latency is the slowest timing tier for DDR3-1333, meaning performance-tuned alternatives at CL7 would theoretically be faster
Compatibility is limited to select Mac models — not a universal DDR3 solution for all Apple hardware
No XMP or overclock profile is relevant here, as Mac EFI does not support manual memory overclocking
At 4GB single-module capacity, reaching 16GB requires four slots, which most DDR3 Mac models do not provide

Frequently Asked Questions

Will this CT4G3S1339M module work in my specific Mac, and how do I verify compatibility?

This module is validated for select Mac systems — not all Macs that use DDR3. The key identifiers are DDR3 SO-DIMM form factor, 1333MHz (PC3-10600) speed, and CL9 latency. Crucial's online compatibility tool cross-references your Mac's model identifier against a validated parts database, which is the most reliable way to confirm fit before purchasing.

Can I run this 4GB module alongside my existing Mac RAM, or must I replace all sticks?

You can mix this module with an existing stick if your Mac has two SO-DIMM slots, but matched pairs running in dual-channel mode deliver measurably better memory bandwidth. For best throughput, install two identical CT4G3S1339M modules for 8GB total in dual-channel configuration.

Is DDR3 1333MHz the same as PC3-10600?

Yes — these are two naming conventions for the same specification. DDR3-1333 refers to the clock speed; PC3-10600 refers to the module's peak bandwidth of approximately 10,600 MB/s. Both designations describe this exact module, and either label on a Mac's memory slot spec confirms compatibility.

Does installing this module void my Mac's warranty?

Apple explicitly supports user RAM upgrades on Mac models with accessible SO-DIMM slots, and Crucial memory meets or exceeds Apple's specifications. For Macs still under AppleCare, RAM upgrades do not void coverage on the rest of the system, though the RAM module itself is not covered by Apple.

What performance improvement should I realistically expect after installing this module?

The measurable benefit depends on your current RAM amount. Going from 4GB to 8GB in a Mac running macOS eliminates swap file usage during typical multitasking — the OS stops writing to the SSD/HDD for memory paging, which reduces latency and extends storage longevity. If you're already at 8GB, the improvement is less pronounced.