Sources and calculation method

SpecPlain tries to separate three things that are often mixed together in buying guides: what a standard defines, what arithmetic can derive, and what a specific product actually implements.

Updated 27 August 2026

Source order

For standards-related claims, the preferred source is the organization that maintains the relevant standard or compliance program. Examples include USB Implementers Forum material for USB and USB Power Delivery, VESA material for DisplayPort behavior, Display Stream Compression and DisplayHDR performance certification, HDMI Licensing Administrator material for HDMI cable categories, CTA and ITU-R material for consumer television and UHDTV terminology, Digital Cinema Initiatives material for digital-cinema image containers, PCI-SIG material for PCI Express signaling and lane behavior, NVM Express material for NVMe storage, SATA-IO material for SATA and SATA M.2 behavior, SNIA material for vendor-neutral SSD workload and endurance methodology, the SD Association for SD card class and interface definitions, NIST references for SI and binary unit conventions, and original manufacturer datasheets for component-specific values.

Manufacturer documentation is preferred over retailer copy for a named product because retailers can simplify, omit, or reformat technical limits. Secondary sources can be useful for context, but they should not replace a primary source when the primary source directly answers the question.

Derived values are shown as derived values

Some useful numbers do not need an external authority because they follow from geometry or unit conversion. For example, display width and height can be calculated from diagonal length and aspect ratio. Pixel density can be calculated from resolution and diagonal size. Watts can be calculated from volts multiplied by amps.

When SpecPlain derives a number, the formula is stated on the page and the browser-side calculator uses the same arithmetic. A calculated value is not presented as though it were copied from a manufacturer specification.

Specification capability is not product behavior

A standard can define what is possible without proving that every product with a familiar connector supports every optional feature. This distinction is especially important with USB-C and M.2. The connector or card shape alone does not establish data rate, display capability, charging power, storage protocol, or host support. A DisplayHDR tier establishes certified test floors but does not replace model-specific measurements across every picture mode or workload. Likewise, a charger's headline wattage does not prove that a particular device will request that power level.

When implementation details matter, SpecPlain tells the reader to check the device or manufacturer documentation instead of filling the gap with an assumption.

Dates matter for evolving standards

Technology standards change. Guides that depend on active standards include an update date and should be rechecked when the standards body publishes a material revision. A source page can remain online for years while the underlying specification gains new releases, so “the source still exists” is not enough by itself.

For example, USB-IF's document library listed USB Power Delivery Specification Revision 3.2 Version 1.2 on 20 May 2026. NVM Express released the NVMe 2.4 specification set on 4 August 2026 and lists the NVMe over PCIe Transport Specification Revision 1.4 as ratified on 31 July 2026. VESA introduced the DisplayHDR True Black 1400 tier on 8 July 2026. PCI-SIG lists PCI Express Base Specification Revision 7.0 as its current approved base specification, while newer draft work is not treated as an approved replacement. A guide can explain older terminology while still identifying the maintained current specification or certification state accurately.

What is intentionally excluded

• Anonymous forum posts as the sole basis for a technical claim.
• Retailer marketing language treated as a standards definition.
• Unverified “universal compatibility” statements.
• Copied comparison tables that add no independent synthesis.
• Benchmarks presented without test conditions.
• Device-specific safety claims inferred from connector shape or wattage alone.

Corrections

If a factual error is confirmed during source review, the affected guide should be corrected. A material correction that changes the practical conclusion should also change the page's update date. Cosmetic wording changes do not need to masquerade as a technical update.

Reference families used by the current library

• USB Implementers Forum for USB Type-C, USB data-rate labeling, cable markings, USB4, and USB Power Delivery.
• USB-IF Document Library for current specification revisions and dated compliance documents.
• VESA DisplayPort FAQ for DisplayPort behavior, DisplayPort over USB-C, and current DisplayPort feature context.
• VESA Display Compression Codecs for DSC visually lossless testing, compression behavior, supported color formats, and adopting display interfaces.
• VESA Certified DisplayHDR for current HDR luminance, contrast, black-level, color and certification-tier criteria.
• Consumer Technology Association (CTA) for consumer-facing 4K Ultra HD television terminology and display definitions.
• International Telecommunication Union, Radiocommunication Sector (ITU-R) for ultra-high-definition television production parameters and standards context.
• Digital Cinema Initiatives (DCI) for digital-cinema 2K and 4K distribution-container definitions.
• HDMI Licensing Administrator for certified HDMI cable categories and official program language.
• PCI-SIG for PCI Express base-revision history, signaling generations, lane widths, and encoding context.
• NVM Express for NVMe base, transport, command-set, and current-revision context.
• SATA-IO for SATA storage naming, M.2 SATA behavior, and form-factor/interface distinctions.
• Storage Networking Industry Association (SNIA) for vendor-neutral SSD workload, performance, endurance, IOPS, throughput, latency, and queue-depth methodology.
• SD Association for SD card speed classes, bus interfaces, capacity families, and host/card compatibility terminology.
• National Institute of Standards and Technology for SI units and prefix conventions.
• Panasonic Energy battery guidance for alkaline, NiMH and button-cell chemistry descriptions, nominal-voltage context, charging cautions, cross-reference information and manufacturer compatibility guidance.
• Energizer Technical Information for primary and rechargeable battery datasheets, IEC cross-references, dimensions, nominal voltage, capacity examples, internal-resistance examples and stated test conditions used by the battery guides.

This page describes the editorial method. Individual guides list the sources most relevant to their own claims.