What Are The True Eye-Fi X2 802.11n Wi-Fi Capabilities?

My experience with the Eye-Fi connected SD camera card has been frustrating, but I wasn’t sure how much blame the company deserved. Uploading massive 14 megapixel photos is going to be slow over a 3G connection using any device, after all. But how fast could the Eye-Fi go on a really great wireless LAN? The company is skimpy with technical specs, but I did manage to figure out just what the Eye-Fi X2 series of cards are capable of in terms of CPU and Wi-Fi performance.

Eye-Fi claims that the X2 card line is capable of “Class 6” read and write speed inside a camera. Class 6 means 6 MB/s, and one might think this is the maximum throughput for the card. Considering that my camera can shoot seven frames per second at 14 megapixels (each image being about 6 MB in size), the Eye-Fi could not handle heavy-duty use when set to transfer all images immediately even if this was the real-world performance one could expect.

This only gets worse when one considers the Eye-Fi Pro X2 card with its RAW image compatibility. My Sony NEX-5 shoots 15 MB RAW images, about three times the size of a “fine” JPEG. This means it would take three times longer to transfer each image, a truly frustrating experience even with the fastest network.

What’s Inside?

Eye-Fi (the company) would rather that we focus on the capabilities of their card rather than its technical components. But any self-respecting geek is going to want to know what makes it tick! I’d rather not cut open my card to get a peek at the chips inside, but Eye-Fi released some official details about the components used in the X2 series of cards, and a quick Google search revealed all that I needed to know.

An official company blog post includes a cutaway image of the inside of the card as well as details about the new X2 chipset. According to Eye-Fi themselves, the X2 line includes a new engine called “Arcturus” which includes a 200 MHz ARM926 processor core. The 926 is part of the 32-bit ARM9 RISC family and includes a digital signal processor, Java acceleration, and local cache. This is not a bad chip, considering the ultra small form factor of the Eye-Fi card.

So the card has enough CPU juice to handle reasonable performance requirements, but what about the Wi-Fi chipset? Eye-Fi doesn’t say too much about the capabilities of the X2 card line, except to boast of their newfound 802.11n compatibility. But the markings on the Wi-Fi chip are clearly visible in Eye-Fi’s official photographs, and a quick search reveals very limited capabilities.

Eye-Fi Wi-Fi

You might want to refer to my 802.11n Overview

The Eye-Fi card uses a Marvell 88W8786 integrated system-on-chip WLAN controller. This is an early 802.11n chip with few features:

• The radio is capable of 2.4 GHz transmissions only, so it is incompatible with 5 GHz 802.11n networks
• Like many portable devices, a single transmit and receive antenna is used so MIMO performance gains are restricted
• The datasheet lists 20/40 MHz coexistence, so it must support 40 MHz channels on 2.4 GHz, a feature that is highly unlikely to be used given the limited number of channels there

In short, the Eye-Fi X2 card is “802.11n in name only” and does not support most of the advanced performance features users might expect. Theoretical data rate with 40 MHz channels is limited to 150 Mb/s, and throughput with 20 MB/s channels tops out at 75 Mb/s, with much less in the real world.

Stephen’s Stance

My own experience shows that the Eye-Fi X2 card takes 3 to 5 seconds to transfer a 6 MB image to my laptop using direct mode. This translates into roughly 12 Mb/s, and represents a best case scenario for image transfer. This drastically reduces the value of the Eye-Fi card when used with high-resolution cameras. Which are exactly the kind of cameras that people might have who are willing to spend more than twice as much for a connected SD card!

Then there’s compatibility. The Eye-Fi card does not support 5 GHz-only 802.11n networks. This isn’t unique – neither does the iPhone 4! But it’s bound to disappoint and frustrate some customers. Products like this are the reason I decided to set my AirPort Express (an either/or base station in terms of radio bands) to use 2.4 GHz even though it is “N-only”.