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Introduction <top>

Collection of speed-related information.

External Interfaces and Speeds

To give an idea of how much time it can take to transfer data over different interfaces. For (e.g.) backups, copying information to other drives / locations than the desktop / laptop / workstation.

Note: numbers below are theorethical and real values may be much lower depending on hardware, software, network congestions, and more. (E.g. A busy Ethernet, local area, network, may actually only provide 10% of theoretical speed.)

Interface Technology Interface Speed Theoretical time to transfer file of different size





10 kB



100 kB



1 MB



10 MB



100 MB


1 GB



10 GB



100 GB



1 TB



SAN - Storage Area Network; typically for enterprise storage solutions but also useful for high-end media workstations
Fibre Channel [7])


200 MB/s

- 4800 MB/s







0.05 s


0.5 s

0.02 s

5 s

0.2 s

50 s

2.1 s

8.3 min

21 s

1.4 h

3.5 m

PAN - Personal Area Network; locally connected external harddrives etc

1.5 Gbps

3.0 Gbps

6.0 Gbps

187.5 MB/s

375 MB/s

750 MB/s








0.03 s


0.27 s


2.7 s


27 s


4.4 min


44 min

ExpressCard, PCI Express mode 2.5 Gbps 312.5 MB/s fast fast fast 0.03 s 0.32 s 3.2 s 32 s 5.3 min 53 min
eSATA[3] (920 Mbps) 115 MB/s



fast 0.09 s 0.9 s 8.7 s 1.45 min 14.5 min 2.4 hrs
FireWire 800 800 Mbps 100 MB/s fast fast 0.01 s 0.1 s 1 s 10 s 1.7 min 16.7 min 2.8 hrs
USB 2.0, ExpressCard, USB mode

480 Mbps

60 MB/s fast fast 0.02 s 0.17 s 1.7 s 16.7 s 2.8 min 27.8 min 4.6 hrs
FireWire 400

400 Mbps

50 MB/s fast fast 0.02 s 0.2 s 2 s 20 s 3.3 min 33 min 5.5 hrs
200x SD Card

240 Mbps

30 MB/s fast fast 0.03 s 0.3 s 3.3 s 33 s 5.5 min[5] (56 min[5]) (9.3 hrs[5])
LAN - Local Area Network; networked devices, Network Attached Storage (NAS), other computers, ...
1000 Base-T 1000 Mbps 125 MB/s fast fast fast 0.08 s 0.8 s 8 s 1.3 min 13 min 2.2 hrs
HomePlug AV [6] (speed, Ref#1)

100 Mbps

- 150 Mbps

as below <-- <-- <-- <-- <-- <-- <-- <-- <--
100 Base-T 100 Mbps 12.5 MB/s fast fast 0.08 s 0.8 s 8 s 1.3 min 13 min 2.2 hrs 22 hrs
10 Base-T 10 Mbps 1.25 MB/s fast 0.08 s 0.8 s 8 s 1.3 s 13 min 2.2 hrs 22 hrs 9.3 days
WAN - Wide Area Network; storage over internet, also download time for users to access content on web site
High-speed broadband 5 Mbps 0.625 MB/s 0.016 s 0.16 s 1.6 s 16 s 2.7 min 27 min 4.4 hrs 1.9 days 18 days
High-speed broadband 2.5 Mbps 0.31 MB/s 0.03 s 0.32 s 3.2 s 32 s 5.4 min 54 min 9 hrs 3.7 days 37 days
3G (US avg)[4] 1.25 Mbps 0.15 MB/s 0.07 s 0.7 s 6.7 s 67 s 11 min 1.8 hrs 18.5 hrs 7.7 days 77 days
Slow High-speed 256 kbps 0.03 MB/s 0.3 s 3 s 30 s 5.6 min 56 min 9.3 hrs 3.8 days 38 days > 1 yr
Dial-up 56 kbps 0.007 MB/s 1.4 s 14 s 2.4 min 24 min 4 hrs 1.7 days 16.5 days 0.5 year 4.5 yrs
[1] Using 8 bits per byte (and 1 Giga (G) = 1000 Mega (M) = 1000 0000 kilo (k))
[2] Internal SATA included for comparison only; not applicable for any external device/storage solution);
times only displayed for the middle speed (3 Gbps)
[3] Actual performance for external SATA drive - "Full SATA speed for external disks (115 MB/s) have been measured with
external RAID enclosures"(wikipedia) (The 920 Mbits/s is calculated from the 115 MB/s.)
[4] 1.2 Mbps from blogs.zdnet.com/BTL/?p=11580 (Jan 22, 2009); using 1.25 as half of next speed up (in this comparison)
[5] SD cards (SDHC) are available up to 32 GB (SDHC, SD std 2.00); Original, 'basic SD cards, std version 1.0: max 1 GB.

Information on HomePlug AV added 2009-10-28.

Ref#1: www.homeplug.org/products/whitepapers/Enhancing_the_Consumer_Experience.pdf - real speed around 100 Mbps.

Ref#2: www.homeplug.org/products/whitepapers/HPAV-White-Paper_050818.pdf - "a 200 Mbps PHY channel and a 150 Mbps
information channel".


Information on Fibre Channel added 2009-10-28.

This table was partly based on information in SATA in comparison with other buses (wikipedia)

Memory Cards





SD Cards (Secure Digital Cards)

Rating Speed (MB/s) SD Class  
6x 0.9 n/a


10x 1.5 n/a  
13x 2.0 2 Class 2: minimum speed 2 MB/s
26x 4.0 4 Class 4: minimum speed 4 MB/s
32x 4.8 4  
40x 6.0 6 Class 6: minimum speed 6 MB/s
66x 10.0 6  
100x 15.0 6  
133x 20.0 6  
150x 22.5 6  
200x 30.0 6 (June 2009 Apple MacBook Pro: 240 Mbit/s, /8 = 30 MB/s)
266x 40.0 6  
300x 45.0 6  


SDHC (Secure Digital High Capacity, SD 2.0) is an extension of the SD standard which increases card's storage capacity up to 32GB.



Which SD card formats work in the SD card slot?

Cards that conform to the SD 1.x and 2.x standards should work.  The SD card slot can use cards that are Standard SD (4 MB to 4 GB) and SDHC (4 GB to 32 GB).  MMC can also be used in this slot.  MiniSD, MicroSD, and higher density formats like MiniSDHC and MicroSDHC can also work with the use of "passive" adapters that conform to the width and thickness specifications listed above.

What is the maximum speed that my computer can use when reading and writing to an SD card in the SD card slot?

Your Macintosh has a maximum speed of 240 Mbit/s for SD media using the SD card slot.  This exceeds the transfer rate of most SD media. Check the packaging that came with your SD media to determine the maximum transfer rate used by that media.

Does the SD slot work with cards that exceed 32 GB?
Yes.  However, most media manufactures preformat the media using common block-and-cluster sizes that do not approach the theoretical limits of a given file system.  Most SD cards use the FAT32 file format.   Preformatted FAT32 SD media is commonly available up to a capacity of 32 GB.  Some smaller capacity cards use the FAT16 file format.  Preformatted FAT16 media is generally available up to a capacity of 2 GB.

Will the SD card slot work with SD cards that use the exFAT file system?


How do I insert media into the SD card slot?

Insert a card with the metal contacts facing down and pointing toward the computer.  Do not force media into the SD card slot.  This may damage the SD card slot.
How does my Mac use the media inserted into the SD card slot?

Your computer recognizes a card inserted into the SD card slot as a USB storage device. The SD card can be mounted, read from, and written to just as any other USB storage device can.
I put the card in the slot, but it did not mount.  What should I do?
Remove the card and insert it again.  Sometimes, if you put the SD card into the slot too slowly, it may not mount properly.
When I try to write content to the card, I get a "cannot be modified" message.  How can I fix this?

This message appears when you attempt to modify the contents of an SD card that is locked using the lock slider on the card.  To edit data on the card, drag the icon representing the device to the trash. When the icon disappears from the desktop, remove the card from the computer.  Adjust the slider tab to unlock the card, then reinsert the card into the slot.

Can I reformat an SD card with Disk Utility?

Yes.  Using Disk Utility, you can partition and format an SD device as FAT32 (using the MS-DOS FAT setting) or Mac OS Extended.  The Mac OS Extended format can only be used on Macintosh systems.  Cards formatted to Mac OS Extended will not be recognized by non-Apple systems.

Can I install Mac OS X on an SD storage device and use it as a startup volume?

Yes.  Change the default partition table to GUID using Disk Utility, and format the card to use the Mac OS Extended file format to do so.

How do I remove a card from the SD card slot?

As with any USB storage device, allow any data transfer to SD media to complete before removing the card.  When removing the card, the best way to insure the integrity of your data is to drag the icon that represents the card into the trash, then remove the card from the slot after the icon disappears from your desktop.

Can I use SDIO (Secure Digital Input Output) cards?

No.  Although SDIO cards are within the width and thickness specifications and should not damage the slot if inserted, they will not be recognized by the computer.

Can I use OS X to see the specifications for the interface hardware and media inserted in the SD card slot?

Yes.  The System Profiler should provide information on the interface hardware and the media you inserted into the slot.  To access the System Profiler, choose About This Mac from the Apple (?) menu.  Click More Info, then select USB in the Hardware section.  A list of USB devices should appear.  Select Internal Memory Card Reader to access information about the interface hardware and the media inserted into the SD card slot.

Can I use the SD card slot while running Windows using Boot Camp?

Yes.  The SD card slot works with Boot Camp in both Windows XP and Windows Vista.


Does anyone know if the SD card slots in the new MBP's are capable of reading SDHC cards or only the older SD cards?
[SDHC is supported, as noted in an Apple announcements discussion in another reader report. -MacInTouch]


References, Read More

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