Secure Digital Memory Cards for Macs

Best Mac SD Cards For High Performance

Combining both speed AND high capacity - those owning more recent Mac mini, Apple MacBook Pro and Air, as well as Aluminum iMac models may have a built-in SD Slot reader. Some connect internally via USB, others interface directly with the PCI bus for faster performance. The slot on Macs accept cards that are either Standard SD (Secure Digital) up to 4 GB, SDHC (Secure Digital High Capacity) 4 GB to 32 GB, and SDXC (Secure Digital Extended Capacity) cards in 32, 64, or 128 GB sizes. Class 10 SD cards have the highest performance. Here are some of the fastest SD cards for Mac currently available:
           
Mac SDXC CardSDXC Card For MacSDHC Card For Mac
SanDisk Extreme Pro SDXC

Up To 95MBps Speed
PNY Elite SDXC Card

Up To 90MBps Speed
Transcend Class 10

Up to 90MBps

Which Macs Have SD Card Slots?

Beginning in 2009 Apple has added a high-speed SD-SDHC slot to these Macintosh computers:

MacBook Pro (13-inch, Mid 2009), MacBook Pro (15-inch, Mid 2009), MacBook Pro (15-inch, 2.53GHz, Mid 2009), MacBook Air (13-inch), iMac (21.5-inch, Late 2009), iMac (27-inch, Late 2009)

Mac mini (Mid 2010) features a rear SDXC slot, backward compatible with SD-SDHC cards.


What Are The Specs of SD Cards for Mac?

See this article at Apple's website for a very good overview of Secure Digital card use on the iMac and MacBook Pro: About the Apple SD Card Slot FAQ. Kingston maintains a great chart identifying the different terms and icons used to identify SD class and speeds - and which devices/needs each type of card is best suited for.

Formatting SD Cards For Mac OSX

SD cards are plain block storage devices and don't imply any specific partition type or file system. As such, other partition schemes than MBR partitioning and DOS/Windows FAT file systems can be used. Under Apple's Mac OS X, SD cards can be partitioned as GUID devices and formatted with the HFS+ file system. Under MS-Windows and some Unix systems, SD cards can be formatted using the NTFS -- and on later versions -- exFAT file system. However most consumer products will expect the default MBR partitioning and FAT16/FAT32 filesystem.

Creating A Bootable SD Card For OSX

When using SD - SDHC flash memory card exclusively for fast Mac backup, optimal Mac to Mac file transfers, or for creating a bootable OSX Tiger, Leopard or Lion, Mavericks or Yosemite Secure Digital startup disk for diagnostic uses, it's important to re-format the card using Apple's Disk Utility. On Intel based Macs you MUST set the partition table type to GUID, and format the card to use the Mac OS Extended format.

Ideally you need a 32GB SDHC or larger card for both the speed and capacity you'll need to install OSX. Leopard needs about 8-12GB depending on Install options chosen. You may opt to do a custom OSX install to minimize Printer Drivers and if installing iLife: Omit GarageBand - it's audio files add several Gigs to an OSX install. Once the install completes, to boot OSX off the SDHC card: Restart and hold down the OPTION key to select the icon for the card as the startup volume.

Using an SD Card As An OSX Boot Disk

Pros:
- SDHC cards offer cheap storage without the need to open up your laptop
- Compact and removable: you can take important applications with you
- Fast Class 6 and higher SDHC cards have rapid data access times
- Data transfer rates remain mostly constant

Cons:
- Your Mac's built-in card reader might be too slow
- Slower SDHC cards aren't really fast compared to SSD drives
- Even a fast SDHC has slower transfer rates than most hard drives
- SD cards MTBF are low, not designed for HEAVY sustained access


Apple Secure Digital Card Specs : SD vs SDHC

SD means Secure Digital which is a non-volatile flash memory card. This memory card is developed by different companies like Panasonic, Toshiba and SanDisk. They are increasingly being used in portable devices like video games, digital cameras, DV camcorders, handheld computers and PDAs. They're vailable in many brands, data transfer speeds, and in different capacities currently from 1MB to 32 GB. This card is proven very successful in the market because of its wafer-thin postage stamp size.

The original maximum 2 GB capacity defined by the SD 1.1 standard wasn’t enough as card sizes grew, so the SD 2.0 or SDHC standard was added. It allows for capacities of up to 32 GB. It is potentially ready for capacities of up to 2 TB. SDXC will be the next iteration of the SD spec, as 32 GB may remain the limit for the SDHC standard. Note that SDHC and SD cards are physically identical from the outside, so be sure your device supports SDHC before purchasing such a card (4 GB and up).

SD was invented by SanDisk in 2001 - and is based on the Multi-Media card (MMC) standard. Technically, SD is similar to MMC, but added digital rights management, and also features a sliding write protection switch. OSX is smart enough to detect the position of the write-lock switch.

It's important to note that SDHC cards are designed for use in SDHC-enabled devices and are not backwards compatible with standard SD-only legacy card readers and devices such as Digital Cameras, MP3 Players, Cell Phones and whatnot. More recent devices support SDHC and its higher capacity and speeds - check the specs of your devices owner's manual to be sure. The iMac's and MacBook Pro's however do support BOTH standard SD and SDHC card reader functions.

For more details on Apple's implementation and technical details of thier SD - SDHC - SDHC card slot support, see this FAQ.

USB SD Flash Card Readers vs Apple Slot

The flash slots on these newer MacBook Pro and iMac computers register as an internal USB Bus device in System Profiler. So for all practical purposes flash Read/Write speeds will be identical to an external USB 2.0 SDHC card reader. At this point, even the fastest Class 10 Secure Digial transfer speeds fall well below USB 2.0's data rate maximum. As NAND flash and the Secure Digital spec evolves, expect USB 3.0 SuperSpeed standard to help take Secure Digital SD card performance to the next level.