Marcus Williams
Marcus Williams covers Mac hardware and repair for Macfax. He spent six years on the bench at an Apple Authorized Service Provider in the Pacific Northwest before going independent, most of that time on logic-board repair, display assembly swaps, and the failure patterns Apple's diagnostics don't surface. He writes about what's inside a Mac, what breaks first, and what a serial number can and can't tell you about a unit's history.
Apple serial number check: the complete guide to looking up a Mac
Apple serial number check is the canonical way to identify a Mac by serial. This is the complete reference for what a Mac serial tells you, where to find one on every Mac family, and how to look up a device across three eras of Apple hardware.
Working with post-2021 Mac serial numbers: what you can and can't decode
Post-2021 Mac serial numbers are randomized 10-character strings that encode nothing. No factory, week, or configuration code. Treat the serial as a dumb token only Apple's database resolves, and lean on the order number, Model Identifier, and A-number plus EMC for offline verification.
What is unified memory on a Mac: UMA, Dynamic Caching, and why RAM is non-upgradeable
Unified memory on a Mac, explained. Apple Silicon's UMA puts CPU, GPU, Neural Engine, and Secure Enclave on one LPDDR pool packaged onto the SoC substrate. That single design choice explains why Mac RAM cannot be upgraded, and why M3's Dynamic Caching is a bigger deal than it sounds.
Mac model number lookup: identifying a Mac from Model ID, A-number, or EMC
A Mac model number lookup playbook for the cases where the serial is missing or illegible. Uses the Model Identifier, A-number, part number, or an EMC plus A-number combination, and the lookup tools that resolve each.
Apple part number decoded: what MNEH3LL/A tells you about a Mac
An Apple part number on a Mac box (MNEH3LL/A and friends) is a SKU: a prefix, a configuration code, a region, and a /A suffix. Here is what each piece tells you, and what it can't.
Apple Coverage Check: how it works and what it shows
Apple Coverage Check is the free serial-lookup tool at checkcoverage.apple.com. It returns the exact model, warranty status, and AppleCare standing for any Mac, iPhone, or iPad. The 'Estimated Purchase Date' is the registration date, not the retail date, which catches buyers and sellers both off-guard.