Secrets of Memory – Exposed!

I just received a piece of plastic, about the size of a postage stamp, containing as much memory as a MacBook Air: 64GB. And that made me wonder: is the 64GB on the Monster Digital SD XC USH-1 Class 10 Vault Series card (got all that?) the same as the  64GB of flash memory inside the Air?

Well, no, it’s not. Not according to Mike Ridling and Mark Morrissey, the President and Head of Storage Technology at Monster Digital.

We started at the beginning: spinning disks. Over the decades, the disks became smaller, and when Apple used the technology in the iPod, 1 in 3 units failed. So, Apple went shopping for a better solution.

At the time, flash drives had been around for about five years, and they were popular, but limited in terms of storage capacity. Camera manufacturers were experimenting with ways to store large number of images in a non-volatile format (that is, when the power goes off, the stored material remains). Then, Apple adopted flash memory for their portable devices–and the market shifted from spinning disks to non-volatile, highly portable, small-sized memory.

What’s inside that SD card? A tiny controller that routes data into and out of the card, and organizes the data on the card’s silicon chip so that it’s accessible and so that the card lasts as long as possible (but not forever).

About six years ago, the Secure Digital Association (SD = Secure Data) standardized the metrics for both memory capacity (64GB) and access speed (Class 10). In fact, the access speed matters–but the information is not always easy to find in your device’s instructions. If you own a big DSLR, buy Class 10 cards. Ditto for any camcorder that costs more than, say, $600-700. A Class 6 card is sufficient for a lesser camcorder or a more modest digital still camera. If you’re using the card in a smart phone or a low resolution camera (say, 2-3 megapixels), then a Class 2 is all you need. Of course, Class 10 cards cost more than Class 2 cards.

If you require higher transfer rates, you’ll want a UHS-1 compatible card, but note that not all of these cards are compatible with all devices. (Monster emphasized that their card works with a lot of different devices.)

Right now, the largest available SD cards are 128GB, but we’ll see 256GB in a year or so. Somehow, through the miracle of engineering, the cards are able to store more data but they don’t become larger (more data is stored within the available space). This means we can expect compatibility for a longer period of years.

Now what about the 64GB SD card in the 64GB MacBook Air? Can I simply double my storage capacity with the purchase of a $200 memory card? Well, sort of. The SATA3 solid state drive in the MacBook Air transfers data at 6GB per second. How does the SD card compare? Well, it’s slower. A lot slower: 80MB per second. This is why the SD card is better suited to, say, storing documents and transferring documents on the Air than, say, running Photoshop. In fact, the 64GB and it’s big sister, the 128GB are ideal for storing either almost 25,000 photographs, nearly 11 hours of HD video, over 1,000 hours of digital music. It’s ideal for use in an HD video camera, for example.

I did ask about whether technology was changing quickly enough to affect my thinking about the next generation Air (coming in May, we think). The answer came as something of a surprise: a new external drive for the Air (and other devices) that would plug into the new Thunderbolt port. Offering a transfer rate of about 10GB per second (1/6 of the internal drive, but a heck of a lot faster than the SD card), this is probably the next step in portable memory for portable computers.

And what about iPad storage? Yeah, it’s kinda messy. Apple really didn’t design iPads for external storage, so the solutions are workarounds. That probably won’t change in the future.

So, I’ve learned to use terms such as “transfer rate” and “Class 10” with some knowledge that I lacked yesterday. And, I’ve gotta say, I have a soft spot for Monster. So, thanks to the two executives who helped me to navigate this technology.


  1. […] per second Thunderbolt speed–Thunderbolt is now standard on every Air. By comparison, you may beef up storage with a 64GB or 128GB SD card, but transfer speed is under 100MB per second, a whole lot slower than other options. Below, […]

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