Card-to-Computer Transfer Speed
This page was last updated on July 25, 2006

If you've attended a Rob Galbraith workflow training session in the last couple of years, you've heard me make the point that, increasingly, a critical workflow bottleneck is the transfer of photos from a stack of CompactFlash or Secure Digital (SD) cards to a waiting computer for editing. This is especially true for photographers working on deadline and/or shooting a lot of photos at an event. But even the casual or low volume photographer can be impacted by this, owing to the ever-increasing size of files produced by today's Canon and Nikon digital SLR cameras, as well as cameras from digital back makers that accept memory cards. Put simply, a slow card and a slow card reader can really bog down a modern workflow. If you're faced with moving pictures from a stack of memory cards to a PC or Mac, and time is of the essence, this section of the CF/SD Performance Database is for you.

The data in the tables linked to below was derived by timing how long it took to transfer about 450MB of Canon EOS-1D Mark II N JPEG and RAW CR2 files from the card to the computer or photo storage device. All cards were secure erased prior to testing. All cards were formatted in the camera, except any SD cards larger than 2GB, which the EOS-1D Mark II N won't format. In that case, the Computer Management utility in Windows XP was used.

The results are arranged alphabetically. The fastest speed for each card is marked in blue.

CompactFlash: Click the graphic above to view a large table of card-to-computer transfer data for readers that accept CompactFlash cards. For best viewing, resize the window that opens to fill your monitor	SD: Click the graphic above to view a table of card-to-computer transfer data for readers that accept SD cards

The Readers

As you might notice if you really study the numbers in the card-to-computer transfer tables above, there are several instances of Reader A producing the same or in some cases identical results to Reader B, even though each comes from a different maker. That's because most of the companies producing readers don't actually manufacture the key components on the inside. Instead, most will source those from a handful of companies globally, sometimes working with the same company to design the overall reader itself too (both the circuit board on the inside and the plastics on the outside).

For instance, the Lexar CompactFlash FireWire reader, model RW019, and the Microtech FireWire CameraMate, utilize a FireWire 400 controller from Oxford Semiconductor. Look at the results for these two readers and you'll see the numbers are within 1-2% of each other for almost all cards. In other words, the performance these readers offer is effectively the same. Most USB 2.0 readers tested use controllers from Genesys Logic, and also provide very similar performance to one another; any differences are likely explained by minor revisions to the controller over time, manufacturing variation or changes requested by the controller customer.

One of the features that distinguishes one controller from another is its level of support for the newest, fastest CompactFlash data timing modes. There are two timing mode acronyms to familiarize yourself with: PIO and UDMA; generally speaking, the higher the number, the faster the potential throughput. In v3.0 of the CompactFlash specification, PIO Mode 6 is the top of the PIO scale, while UDMA Mode 4 is the top of the UDMA scale. As of this writing, there are numerous CompactFlash cards and readers we've tested that support up to PIO Mode 6; combine a PIO Mode 6-capable card with a PIO Mode 6-capable reader and, generally speaking, fast transfers are the result. Look at the CompactFlash results table, locate a card that clocks in between 15-17MB/second across a number of readers and you will have found PIO Mode 6 in action.

A small handful of cards we've tested are capable of UDMA Mode 2. These particular cards deliver between 16-20MB/second throughput in UDMA 2 mode. One line of CompactFlash, SanDisk Extreme IV, supports UDMA Mode 4, and as a result is capable of over 38MB/second in our testing.

All this data timing mode gobbledygook seems to be less of a factor for SD right now, as most of the readers that accept SD we've tested are designed to take advantage of the fastest transfer methods outlined in v1.1 and v2.0 of the SD specification. It's not expected that the SD specification will be revised to significantly boost potential read speed until sometime in 2007.

Therefore, for readers that accept CompactFlash, the reader's description lists the fastest data timing mode supported for that format. We'll do the same for SD readers at some future point when it becomes necessary, based on the evolution of SD.

D-Link DUB CR-200 This is a combination 3-port USB 2.0 hub and USB 2.0 card reader that accepts CompactFlash, SD and many other formats. The fastest CompactFlash data timing mode supported is unknown, but is probably PIO Mode 4.

IOGEAR Universal Memory Bank GFR280 This USB 2.0 reader accepts CompactFlash, SD and many other formats. The fastest CompactFlash data timing mode supported is unknown, but is probably PIO Mode 4.

Jobo 23in1 SE9231 This USB 2.0 reader accepts CompactFlash, SD and many other formats and is particularly compact for a multi-format reader. The fastest CompactFlash data timing mode supported is PIO Mode 6.

Kingston 15-in-1 This USB 2.0 reader accepts CompactFlash, SD and many other formats. The fastest CompactFlash data timing mode supported is PIO Mode 6.

Lexar CF, model RW018 This USB 2.0 reader accepts CompactFlash only. The fastest CompactFlash data timing mode supported is unknown, but is probably PIO Mode 4.

Lexar Professional CF, model RW025 This USB 2.0 reader accepts CompactFlash only. It features a stackable design that enables several Lexar Pro CF readers to perch on top of each other as well as the companion Lexar Professional 4-Port USB 2.0 Hub, which is also stackable. The card insert/eject mechanism is overly stiff. The fastest CompactFlash data timing mode supported is PIO Mode 6.

OnSpec reference board w/xSil 251 chipset This is a glimpse into the future. OnSpec is a controller design company whose xSil 251 chipset supports up to PIO Mode 6 and up to UDMA Mode 4, which makes it the only chipset we know of that has full support for both protocols.

We've tested this controller embedded into a reference board the company supplies in a design kit to its customers. OnSpec's Bryan Chin indicates there are several readers being designed around the xSil 251 that should emerge on store shelves at some point. One of the first such readers is expected to come from Compuapps. Called the OmniFlash USB 2.0 UDMA 40 UnoCF Reader/Writer, the company is now accepting pre-orders but the reader is not yet available. As soon as it ships, we'll test it and posts the results here.

SanDisk Extreme FireWire CF This FireWire 800/400 reader accepts CompactFlash only. It supports UDMA up to Mode 4 and PIO up to Mode 4. This is the only shipping (as of July 21, 2006) reader we know of to offer UDMA support. It utilizes a controller from Oxford Semiconductor.

SanDisk Extreme USB 2.0 This USB 2.0 reader accepts CompactFlash, SD and several other formats. The fastest CompactFlash data timing mode supported is PIO Mode 6.

SanDisk ImageMate CF This USB 2.0 reader accepts CompactFlash only. The fastest CompactFlash data timing mode supported is PIO Mode 6.

SanDisk ImageMate 5-in-1 This USB 2.0 reader accepts SD and several other formats.

Smartdisk Dazzle Thunderbolt CF This USB 2.0 reader accepts CompactFlash only. The fastest CompactFlash data timing mode supported is PIO Mode 6.

Smartdisk Dazzle Thunderbolt SD This USB 2.0 reader accepts SD and several other formats.

Transcend Portable Multi-Card TS-RD13 This USB 2.0 reader accepts CompactFlash, SD and many other formats. The fastest CompactFlash data timing mode supported is PIO Mode 6.

Lexar CF (model RW019) FireWire This FireWire 400 reader accepts CompactFlash only. It utilizes a controller from Oxford Semiconductor. The fastest CompactFlash data timing mode supported is PIO Mode 4.

Lexar Pro CF (model RW024) FireWire This FireWire 400 reader accepts CompactFlash only. It features a stackable design that enables several Lexar Pro CF FireWire readers to perch on top of each other and daisy-chain together with included ultra-short FireWire cables. The card insert/eject mechanism is overly stiff. It utilizes a controller from Initio. The fastest CompactFlash data timing mode supported is PIO Mode 4.

Microtech FireWire CameraMate This FireWire 400 reader accepts CompactFlash only. It utilizes a controller from Oxford Semiconductor. The fastest CompactFlash data timing mode supported is PIO Mode 4. This is the only FireWire or USB 2.0 reader tested whose cable is permanently attached. The FireWire CameraMate is also the only one that's long discontinued, but as it seems to still be available (we purchased it in May 2006) and is a decent-performing reader overall, we chose to include it here.

Hagiwara ExpressCard Adapter CF This ExpressCard 54 adapter accepts CompactFlash only. The fastest CompactFlash data timing mode supported is unknown, but is probably PIO Mode 4.

Delkin CardBus 32 Adapter CF This PC Card adapter accepts CompactFlash only. The fastest CompactFlash data timing mode supported is unknown, but is probably PIO Mode 4. The identical adapter is available from Lexar as the High-Speed 32-bit CardBus Reader. 

Nexto CF OTG ND-2300 photo storage device (firmware v1.0.3) This isn't a reader per se but a standalone photo storage device comprised of a CompactFlash card slot, internal hard drive and LCD menu screen. The fastest CompactFlash data timing mode supported is PIO Mode 4.

Panasonic Pro High Speed CardBus Adapter SD This Windows-only PC Card adapter accepts SD cards.

The Computers

To accommodate the range of readers included in this section of the CF/SD Performance Database, we've settled on a mix of Mac and PC computers, both desktop and laptop.

The computers were selected with two goals in mind. The first goal - compatibility - is an obvious one: it's not possible to test an ExpressCard reader, for example, unless one of the computers has an ExpressCard slot. Second, we wanted to minimize any avoidable performance bottlenecks, so that the true capabilities of a given card in a given reader would shine through. For that reason, we've opted to test all FireWire readers on a Mac, since we've not yet found a Windows PC either with built-in FireWire or an add-in card that can equal the built-in FireWire of a Power Mac G5. Conversely, we haven't tested a Mac that's been able to quite match the speedy USB 2.0 throughput of a Windows PC, one sporting an Intel 9xx series motherboard specifically. So, all USB reader testing has been done on a PC with just such a motherboard.

Does this mean that the USB 2.0 card reader results are only applicable to Windows folks using non-Apple hardware? Not at all. In absolute terms, the only way to achieve the same throughput numbers shown in the tables is to be running a similar Windows XP system configured in a similar manner. We've tried the built-in USB on more than a dozen modern computers, including a Quad G5 Mac, iMac and MacBook Pro, the latter two sporting Apple/Intel motherboards, and none delivers the same throughput as the USB 2.0 ports embedded on the Intel D945GTP motherboard of our PC test machine. And, as noted above, we've tried to set up all systems so that we're eeking out maximum data transfer rates while still having the data be representative of real-world conditions (in other words, no benchmarking software).

Ultimately, however, we've sought absolute performance from all cards and readers so that you will have a clearer picture of the relative performance of one reader vs another with a given memory card. And for USB 2.0 readers specifically, the relative performance stays roughly the same when the attached computer is a modern Mac as well, though there is some leveling off of performance with the very fastest cards in the very fastest readers.

The FireWire story isn't nearly as pretty. While we've seen impressively-consistent FireWire performance across a range of Macs produced in the last several years, the same can't be said of PCs, both laptops with built-in FireWire 400 ports as well as PC desktops with an add-in FireWire 400 PCI card. To give you an idea of the range of variability, a FireWire reader/CompactFlash card combo capable of over 14MB/second when connected to a built-in FireWire 400 port on newer Apple hardware produces anywhere between 3MB/sec and just under 13MB/sec on all non-Apple desktop setups we've tried. The built-in FireWire on the small handful of PC laptops we've tested has been equally variable and even more unimpressive; one model topped out at a painfully slow 1.2MB/second in fact.

Our experience with FireWire 800 and Windows has been better: the OWC Mercury FireWire 800 PCI card is a decent counterpart to the only FireWire 800 reader we've seen, the SanDisk Extreme FireWire Reader. Connect any FireWire 400 reader to this add-in card, however, and transfer rates are only a fraction of what the reader is capable of. Not surprisingly, for the CF/SD Performance Database we've opted to test FireWire readers on the Mac only for now.

Note: On our To Do list is to test a newer non-Apple desktop PC with built-in, on-the-motherboard FireWire 400/800 . That might reveal a PC system whose FireWire performance matches the built-in FireWire of Apple hardware. Or not. We don't know because we haven't tried one yet.

We put the Delkin CardBus 32 Adapter through its paces on both Mac and PC laptops. That's because the performance capabilities of this reader are quite different whether it's inserted into the PC Card slot of a Windows PC or Powerbook.

The computers used for this section of the CF/SD Performance Database are:

Custom-built PC from MDG featuring an Intel D945GTP Desktop Board The selection of this particular component for the computer wasn't arbitrary; after being told by three different USB reader chipset makers that Intel 9xx series motherboards are what they favour internally, owing to their stellar USB 2.0 implementation, it was clear that the next Windows desktop PC here had to be similarly-equipped. Our custom PC is also outfitted with a P4/3.4GHz processor, 2GB RAM, a Radeon X300 graphics card and 160GB RAID 0 hard drive array. The operating system is Windows XP SP2.

Apple Power Mac G5/Dual 2.0GHz For card-to-computer transfers with the FireWire readers tested, this early G5 tower is as fast as any of the newest Macs we have access to, including a Quad G5 or Intel-based Mac, so we've stuck with it for this purpose. It has twin G5 processors running at 2GHz, 2.5GB RAM, an ATI Radeon X800 XT Mac Edition graphics card and 500GB RAID 0 hard drive array. The operating system is Mac OS X 10.4.7.

Dell Inspiron 6400 One of the first laptops from a mainstream PC maker to include an ExpressCard 54 slot, it  also sports a 2.0GHz Intel Core Duo processor, 2GB RAM, an ATI Mobility Radeon X1300 graphics card and 80GB drive. The operating system is Windows XP SP2.

Toshiba Satellite A70 Prior to the introduction of laptops with Intel Core Duo inside, this was one of the quickest portable photo processing machines around. It features a P4/3.33GHz processor, 1.5GB RAM, an ATI Mobility Radeon 9000 graphics card and 80GB drive. The operating system is Windows XP SP2.

Apple PowerBook G4 15 inch This was one of the last Apple laptops to include a PC Card slot before the company moved to ExpressCard 34 in their new portable Macs. This computer has a 1.67GHz G4 processor, 2GB RAM, an ATI Mobility Radeon 9700 video card and 100GB drive. The operating system is Mac OS X 10.4.7.