When putting together your next single-board computer project, you're probably tempted to get one of the newest SD cards with the fastest speeds. After all, a new Pi project deserves quality components. However, before you purchase that ultra-high-speed SD card, you may want to take a closer look at your Raspberry Pi's specs.

While speedy SD cards typically mean faster load times, high-speed SD cards are more useful for photo and video cameras compared to single-board computers. While some Pi projects can benefit from a quicker SD, you don't need the highest storage speeds for a few key reasons.

Raspberry Pi doesn't support advanced SD features

SBCs are somewhat limited devices, after all.

Whether you're using an older Raspberry Pi like the Pi 4 or Pi 3, older Pis don't support all the advanced specifications of the fastest A2-class SD cards. So that fancy new SD card won't be performing at its top speeds. You can use an A2 SD card on a Raspberry Pi, but it will perform at lower speeds, closer to A1 performance, which makes it pointless to use an A2-class SD on an older Pi.

The Raspberry Pi 5 can benefit from an A2 SD card, as long as you update to the latest release of Raspberry Pi OS or update your Pi OS install with the latest software packages. But if your Pi project requires a different OS from the proprietary Raspberry Pi OS Linux distribution, you might have some issues getting the top speed out of that A2 SD card even on a new Pi.

Raspberry Pis can bottleneck

The Pi's built-in SD reader has a maximum speed

The Raspberry Pi's built-in SD card reader does have a maximum read speed. This is significantly lower than the maximum speed of the fastest SD cards, so you can run into a hardware bottleneck if you use an SD card that's too fast for your Pi to read.

Some older Raspberry Pis are limited to just 50 MB/s, but even the Raspberry Pi 5's maximum speed is lower than that of your average A2 SD card. The Pi 5's built-in card reader is capped at UHS-I SDR104, limiting its top read speed to about 104 MB/s, while some A2 SD cards can reach over 150 MB/s. While you can get an A2 class SD or micro-SD card for your Raspberry Pi that doesn't beat the Pi's card reader speeds, it can take some research to find the best SD card for a Raspberry Pi, and you'll want to make sure you know just what speeds your particular Pi model can handle.

The SD card you should buy instead

The best bang for your buck, that won't break your Pi in the long run

Sure, you can look through all the lists of the best Raspberry Pi SD cards to find an A2-class SD that fits within your Pi's maximum threshold, but that only works if you've got a Pi 5 and are running the latest version of Raspberry Pi OS for your SBC project so you can take proper advantage of the A2's top speeds.

If you're using an older Pi or don't want to risk a hardware bottleneck, an A1-rated SD card gives you the best bang for your buck. And you don't need to worry about your Pi not supporting its high-performance features or top speed. An A1-class SD isn't going to be held back by the hardware, even on an older Pi like a Pi 1 or Pi 3. So an older A1 SD isn't just a better bargain, it's also the better choice from a compatibility standpoint.

You can always boot from an SSD

If you need more speed

Some Pi projects require much faster boot speeds, however. And that's where an A1 SD card will be a real pain point. While you can pay up for the A2-class SD, there's a better option.

After all, even the Pi 5 tops out at about 104 MB/s. This isn't too shabby, but it's not quite fast enough if you're planning to use your SBC for more intensive workloads, like using your Pi as a personal Git server. In that case, even running the Pi 5 at its maximum SD read speed won't cut it.

So you're better off booting your Pi from an SSD instead of a built-in SD card. This might seem a bit counterintuitive since you need to connect an external SSD to the single-board computer, but this allows you to bypass the SD card reader's speed limitations entirely. And even a cheap SSD will have faster read and write speeds than a top-end A2 microSD.

You can even get a little fancy with this if you've got a Pi 5 for your project by making use of the PCIe‑to‑M.2 HAT, so the SATA SSD sits on the Pi 5, and you don't need to worry about any extra cables, wires, or enclosures. And a cheap 2.5-inch SATA drive or M.2 SATA SSD is easily a better bargain than a high-end microSD card. So it'll get you better performance and a better value all at once.