Buying SD cards: A1, A2, U3, trusted brands and spotting fakes
Quick answer: Buy a known brand (SanDisk, Samsung, Kingston, Lexar) from a proper seller, look for A2 and U3 or V30 on the label, get one size bigger than your build, and test it with H2testw before you trust a big build to it.
The SD card is the cheapest part of a retro build and the one most likely to ruin your weekend. A slow or fake card causes freezes, corrupted saves and builds that randomly stop booting. Spend a few quid more here and you skip most of the pain.
What the symbols on the card mean
Cards are covered in tiny logos. Only a few matter for us:
| Mark | What it means | Do you want it? |
|---|---|---|
| A1 | App Performance Class 1: handles lots of small reads and writes quickly | Fine |
| A2 | App Performance Class 2: faster again at small reads and writes | Best choice |
| U3 | UHS Speed Class 3: at least 30MB/s when writing | Yes |
| V30 | Video Speed Class 30: also at least 30MB/s writing | Yes |
| U1 / Class 10 | At least 10MB/s writing | Works, but slower |
Why A1 and A2 matter: a retro build is not one big video file. It is thousands of little files (games, artwork, settings, saves). The A rating is about exactly that kind of work, so menus scroll smoother and games load quicker. Some older devices do not use every A2 trick, but an A2 card works fine everywhere.
Brands we trust
- SanDisk (Extreme and Ultra ranges)
- Samsung (EVO and PRO ranges)
- Kingston (Canvas range)
- Lexar
Buy from a proper seller: the brand’s own store or a big retailer selling the card itself, not a random marketplace seller with a name made of capital letters.
How big?
Always get one size bigger than the build. Cards with the same label are not all exactly the same size, so a 256GB image may not fit a 256GB card. Our image will not fit article explains why, and What Size SD Card or Drive Do I Need? helps you match builds to cards.
Spotting a fake
Fake cards are rewired to report a huge size while holding far less. Everything seems fine until you write past the real size, then files quietly turn to garbage. Warning signs:
- The price is silly. A “2TB” card for the price of a pizza is a fake, every time.
- Odd branding. Spelling mistakes, a brand you have never heard of, wobbly printing, or a capacity the brand does not make.
- Writes fail near the end, or the build boots once then falls over.
Test a new card (5 minutes of work, one long wait)
- On Windows, get H2testw (on Mac or Linux, the equivalent is F3).
- Put the empty card in your PC, open H2testw, pick the card’s drive letter and choose all available space.
- Click Write + Verify and leave it. A big card can take hours.
- “Test finished without errors” means the card is genuine. Any errors or “data lost” means return it.
Test before you write a build, because writing the image wipes the card anyway.
Cards we recommend
These are affiliate links, so buying through them supports Arcade Punks at no extra cost to you:
- 128GB A2 microSD cards for small, focused builds
- 256GB A2 microSD cards, the sweet spot for most Pi builds
- 512GB A2 microSD cards for bigger builds
- 1TB A2 microSD cards for the big all-in-one builds
- 1.5TB microSD cards for monster builds
Going bigger than a card makes sense? An SSD is faster and tougher for large builds. See writing to an SSD or hard drive.
Still stuck? Read writing an SD card or the kit you need, or ask in our Discord.