How to read a DRAM part number (and what actually decides compatibility)

Why part numbers matter more than the brand name

When a DRAM line goes on allocation or reaches end-of-life, most teams start by matching the original manufacturer's part number. That is the right instinct — but the part number is a compressed specification, and two parts that look nearly identical can differ in ways that decide whether your board boots at the first try or fails at temperature.

This guide walks through the fields that actually matter when you are choosing a PIN2PIN alternative, using real examples from our own cross-reference table of 245 memory part pages. You can search any of them in our cross-reference tool.

The six fields that decide compatibility

• Density — the total capacity in Gbit (the "1G", "2G", "4G", "8G" in the marking). A different density is a different part; it cannot be treated as a drop-in even when the package is identical.
• Organization / word width — written as 128Mx8, 64Mx16, 256Mx16. Density stays the same while the width changes how many DQ lines the device presents: x8 devices offer 8 data lines, x16 devices offer 16. The number of banks and the layout of the ball map follow from this, so it is the field that most often breaks a "same density" assumption.
• Speed grade — DDR3-1600, DDR3-1866, DDR3-2133; DDR4-2666, DDR4-2933, DDR4-3200. Same silicon family, different timing bins.
• Voltage — DDR3 comes in 1.5 V standard and 1.35 V low-voltage ("L"/"U" codes at most vendors); DDR4 is 1.2 V; LPDDR4/X uses a multi-rail scheme such as 1.8/1.1/1.1 V. Mixing voltage families is not a drop-in.
• Package — 96-ball VFBGA for DDR3, 78/96-ball FBGA for DDR4, 200-ball VFBGA for LPDDR4. A "96-ball" DDR3 device is mechanically interchangeable across brands; the marking conventions are not.
• Temperature grade and packing suffix — commercial (0 to +95 °C) versus industrial (−40 to +95 °C), plus tape-and-reel or tray suffixes. The die can be identical while the grade is not.

Worked examples from our own table

Take the Samsung DDR3 device K4B1G0846I-BCK0. Read as data, it is a 1 Gbit, 128Mx8, DDR3-1600, 1.5 V, VFBGA-96 part in commercial grade — which is exactly how our cross-reference row records it, mapped to HGD31G08S16. The same Samsung family also ships a faster bin, K4B1G0846I-BCNB (DDR3-2133), and we map that to a separate part, HGD31G08S21, because the speed bin is part of the specification.

Change the width and you change the part. K4B1G1646I-BCK0 is also 1 Gbit and DDR3-1600, but it is 64Mx16 — 16 data lines instead of 8 — and maps to HGD31G16S16. Teams that treat "1 Gbit DDR3" as a single specification are usually tripped up here.

Manufacturer conventions differ, which is why we keep the comparison in a structured table rather than in a decoder chart:

All six rows above are live pages in our cross-reference — click any HGCHIPS part number to see its full parameter set and the original part it replaces.

Where part numbers stop being reliable

A part number identifies a specification, not a physical lot. Three things routinely change underneath an unchanged marking:

• Die revisions. Vendors re-spin dies while keeping the marketing part number. A DDR4 "C-die" and "D-die" of the same nominal speed can behave differently in timing margin — which is why a functional test on your own platform, not the datasheet comparison alone, is what finally qualifies a part.
• Letter grades and package variants. Suffixes such as P / A / T or reel-versus-tray indicate grade and packing, not function. Our ADI µModule mapping is a good example: the same HG module covers two footprint variants, so we confirm the exact marking on your BOM line by line.
• Mixed lots from open-market sources. Two reels of the same part number can carry different die revisions. Per-lot test records are what make this visible; that is why our parts ship with lot-level inspection and validation data.

How we use this when you send a BOM

Send a part number (or a full BOM) and we do the field-by-field comparison — density, organization, speed bin, voltage, package, temperature grade — against the original manufacturer's public datasheet, then report the matching HGCHIPS part with its parameter table. Samples start at 10 pcs, with the sample cost credited against your first production order. Where the original is still the better answer, we say so: our original-brand stock line covers Samsung, SK Hynix, Micron, Nanya and ESMT parts for urgent and end-of-life needs.

Ready to decode your own line? Search it in the cross-reference tool, or browse all part pages.