Notes on Macs.
Apple Silicon benchmarks, buying guides, fraud explainers, and what we see in the diagnostic data.
What to check when buying a Mac: a glossary for buyers and sellers
What to check when buying a Mac, term by term: Activation Lock, MDM, ADE, iCloud account state, Secure Enclave, FileVault, SIP, Secure Boot, unified memory, and Apple Coverage Check, each with a one-line verification pointer.
Apple Diagnostics reference codes: every prefix and what it actually means
Apple Diagnostics reports a three-letter prefix plus three digits. ADP000 means clean. Every other prefix maps to a specific subsystem on Apple's published reference list, with very different cost implications depending on whether the issue is the battery, a soldered memory module, the display assembly, or a sensor trace severed by liquid ingress.
Blank Board Serializer: what happens to a Mac serial after a logic-board swap
Blank Board Serializer is the Apple tool that writes a Mac's original serial onto a replacement logic board. Policy says the serial doesn't change. In practice, a small fraction of repairs leave it blank or wrong, and once a board carries any serial, it generally can't be re-flashed.
Mac LLM cluster: the complete 2026 guide to home Mac inference
Mac LLM cluster reference for 2026. Two December 2025 changes (RDMA over Thunderbolt 5 in macOS 26.2 and EXO 1.0) put trillion-parameter inference inside a 1 kW residential envelope. A 4-node M3 Ultra Mac Studio cluster runs Kimi K2 Thinking at 25 tok/s for under $40,000.
MacBook battery cycle count and resale value: what buyers pay for
MacBook battery cycle count moves resale price by 5 to 20 percent. Under 300 cycles adds 5 to 10 percent. Over 800 takes 10 to 20 percent off, regardless of cosmetics. Plus the diagnostic and grade factors buyers actually check.
Apple Coverage Check: the complete 2026 guide
Apple Coverage Check at checkcoverage.apple.com is now branded AppleCare & Warranty. This is the complete reference for what every result state means, what each field on a valid result actually says, and what the tool deliberately does not show.
How to sell a MacBook or Mac: the complete 2026 seller's guide
How to sell a MacBook or Mac in 2026, end to end. Platform choice, pre-sale prep, timing, pricing, listing, payment, and shipping. Skipping the iCloud sign-out before erasing is the largest preventable failure mode.
Apple Diagnostics: how to start the test on Apple Silicon and Intel Macs
Apple Silicon Macs start Apple Diagnostics from the startup-options window with Command-D, not the old hold-D-at-boot keystroke. Here's the exact sequence on both architectures and what to disconnect before you start.
LL/A meaning on a Mac: how Apple region codes work and what they don't change
The LL/A, B/A, J/A suffix on a Mac part number identifies the market the unit was packaged for. It encodes keyboard layout, power adapter, and a few regulatory bits. It does not change the chip, RAM, or storage.
Apple Silicon for local LLM inference: the complete 2026 guide
How to run an LLM locally on a Mac in 2026. Apple Silicon is the only consumer platform that fits 70B dense and 100B to 700B MoE models on one machine, and the only one that loses 3x to 10x on prompt processing. Capacity-first buying framework, with the numbers.
Activation Lock on Mac: the complete guide
Activation Lock arms automatically the moment you turn Find My Mac on, on any T2 (2018-2020 Intel) or Apple silicon Mac running Catalina or later. Here is how the lock is enforced, the four screens that get confused for it, every legitimate clear, and the in-person check that holds up before paying.
MacBook depreciation rate: the Apple Silicon curve, year by year
MacBook depreciation rate on Apple Silicon: median residual is 88% at 6 months, 78% at 12, 58% at 24, and 44% at 48. The full year-by-year curve, three regimes inside it, and where it bends.
How to buy a refurbished or pre-owned Mac in 2026: the complete guide
How to buy a refurbished or pre-owned Mac in 2026. Apple Certified Refurbished vs Back Market vs OWC, the three provenance checks before paying, the inspection protocol, and the time-bounded recourse windows.
Mac diagnostics: the complete 2026 guide
Apple Diagnostics is the only Apple-sanctioned hardware test built into every Mac since 2013, and a clean run returns reference code ADP000. This is the full 2026 guide: how to run it, the technician-only stack that isn't accessible to you, and the third-party tools (CoconutBattery, smartctl, DriveDx, EtreCheck) that fill the gaps Apple deliberately hides.
A1278 MacBook Pro: how to tell which year you actually have
The A1278 13-inch MacBook Pro chassis shipped from late 2008 through mid-2012. Externally identical year to year, internally five different logic boards spanning two Intel socket transitions. The EMC number is the only clean way to tell them apart.
Used Mac prices in 2026: a complete guide to the aftermarket
Used Mac prices in May 2026 across every model family, channel, and trade-in comparison. Apple Silicon residuals are inverting the historical decline, Apple Trade In pays roughly half of peer-to-peer, and three macro forces explain why.
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.
Why eBay Authenticity Guarantee covers watches and sneakers but not Macs
eBay Authenticity Guarantee inspects watches, sneakers, handbags, jewelry, and trading cards before delivery, but not Macs. Here is the category logic behind the exclusion and the Money Back Guarantee mechanics that remain for Mac listings.
DFU restore at scale: parallel wipe rigs for Apple Silicon Mac refurb
DFU restore at scale on Apple Silicon: how small refurbishers run 5 to 16 Macs through a single host. Cabling, port selection, the DFU entry sequence, and where parallel rigs from Acroname and Cambrionix actually pay off.
Swappa Mac listing requirements: serial verification and photo codes
Swappa Mac listing requirements: every listing is manually reviewed before it goes live, and three checks drive almost all first-pass rejections. Serial verification, a handwritten verification code, and exact variant matching against the catalog.
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.
Activation Lock check on a Mac: how to verify it's off before buying
Activation Lock on a Mac can only be verified by observing the Mac's boot state. There is no public server-side check, no Apple-hosted lookup, and no screenshot a seller can send that counts as proof. The only reliable evidence is the seller running Erase All Content and Settings on video and reaching the Setup Assistant "Hello" screen without a lock prompt.
eBay empty-box scam on a MacBook sale: the four-defense stack for sellers
The eBay empty-box scam (item not as described) is the most prevalent fraud against high-value MacBook sales. A packing video, carrier-stamped weight, signature confirmation, and buyer vetting are the four defenses that hold up under appeal.
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.
Back Market vs Reebelo: which refurbished Mac marketplace to buy from
Back Market vs Reebelo for a refurbished Mac comes down to inspection scope, battery floors, OEM-parts guarantees, and accidental-damage cover. Both run curated-refurbisher models with 12-month warranties and 30-day returns; the differences at the edges decide specific listings.
Swappa fees explained: what you actually net on a Mac sale
Swappa fees on a Mac sale: 3% to the buyer plus 3% to the seller, both on the Ask Price, on top of PayPal or Stripe processing. Here is the math on what a Mac seller actually pockets.
Find My Mac and Activation Lock: turning off the iCloud switch before selling
Find My Mac is the iCloud feature that lets the owner locate, lock, or remotely erase the Mac, and on every T2 or Apple silicon Mac it is also the switch that controls Activation Lock. Turning Find My off is what releases the device for sale.
Mac Studio case-swap fraud: weigh one and check Activation Lock before buying
Mac Studio case-swap fraud transplants lower-spec or Activation-Locked boards into clean-serial chassis. A digital postal scale catches the Max-in-Ultra swap because copper cooling cannot be faked; a buyer-side Activation Lock check catches the rest.
Apple Certified Refurbished vs Back Market vs OWC: where to buy a refurbished Mac
Apple Certified Refurbished vs Back Market vs OWC: side-by-side comparison on warranty length, return window, typical discount, grading standards, and the configurations each refurbished Mac channel actually carries.
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 Certified Refurbished vs buying a used Mac from a private seller
Apple Certified Refurbished Macs ship at around 15% off new with a one-year warranty and 14-day returns; private-party listings sit 30 to 50% below new and shift the verification work to the buyer. Here is what each side delivers on warranty, parts, and counterparty risk.
Facebook Marketplace seller scams on Mac sales: Zelle, fake payments, and cloned listings
Facebook Marketplace seller scams on Mac sales: the payment-side patterns that target Mac sellers, the signals that identify each, and the one procedural rule that defeats most of them.
What is FileVault on a Mac
FileVault on a Mac is macOS's built-in full-disk encryption. On Apple silicon and T2 Macs it toggles instantly because the SSD is already hardware-encrypted by the Secure Enclave; on older Intel Macs it triggers a multi-hour software encryption pass.
iCloud unlock and MDM bypass on Mac: why every service is a scam
iCloud locked Macs and MDM-bound Macs cannot be unlocked by a third party. Apple sells no consumer iCloud removal product, and every "bypass" service sells the appearance of a clean Mac, not a clean Mac. Activation Lock and ABM/ASM enrollment are enforced on Apple's servers, so every client-side workaround unwinds the moment the device re-contacts Apple.
MacBook Pro stage light effect: the flexgate inspection and what to check before buying
MacBook Pro stage light effect is the flexgate-era defect that shows up as a row of bright and dim patches along the bottom edge of the display, often only past 80 degrees of lid opening. The single most diagnostic check before buying a MacBook Pro, plus the rest of the in-person inspection.
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.
How to buy a used Mac safely: every verification option compared
How to buy a used Mac safely starts with chaining Apple Coverage Check, Apple Diagnostics, in-person Activation Lock and MDM verification, CoconutBattery, and DriveDx. Here is every consumer-accessible option compared on what it delivers and where it falls short.