On paper ExpressCard readers are fast but in practice other factors can limit performance
Price: UK: £21, USA: $39, Europe: €28
In this review we have a look at the Lexar Professional ExpressCard CompactFlash Reader. This is compatible with Apple Mac or Windows laptops or other PCs fitted with either an ExpressCard 34 or 54 (mm) interface slot. Most laptops don't feature an integrated CF card reader any more, so from a practical point of view an ExpressCard reader is useful if your camera uses CF cards. It also promises, on paper, much faster transfer rates to and from your compact flash memory cards than standard USB 2.0 High Speed card readers. Our test results show that this can be the case, but not always.
This article does get slightly technical... to say the least. If you simply wish to read the conclusion and avoid the jargon, jump there now.
Lexar's ExpressCard reader is fully compliant with the PCI Express (PCIe) bus, which many new laptops offer. Put simply, this is the replacement for the old PC Card, or PCMCIA, system of expansion cards that operated over the old and much slower PCI CardBus. Not all ExpressCards are fully PCIe compliant and many only utilise USB 2.0 High Speed connectivity. ExpressCards working over PCIe have a theoretical bandwidth of 2.5Gb (gigabits) per second, compared to 480Mb (megabits) per second for USB 2.0 High Speed. In other words ExpressCards can be up to 5.3x faster than USB 2.0 High Speed.
Late last year we reviewed Lexar's fastest Compact Flash memory card, the Lexar Pro UDMA 600x. Rated at 600x (1x is equivalent to 150K bytes per second, or the data transfer speed of the original compact disc specification), UDMA 600x cards have a theoretical data transfer performance of just under 88 megabytes per second (MB/sec). The UDMA 6 standard that these cards are built to has a theoretical performance limit of 133MB/second. USB 2.0 High Speed has a theoretical speed limit of 480Mb/sec, or 60MB/sec, and that's slower than a UDMA 6 600x card, like the Lexar Pro UDMA 600x compact flash card. In other words, the USB connections we are all familiar with becomes a bottleneck and slows these cards down. Even if you have a fast connection for your card reader, system overheads and other bottlenecks have an effect on real world transfer rates. To test the Lexar Pro 600x UDMA card we used a PCI Express FireWire 800 interface card reader on a reasonably powerful desktop PC. The FireWire 800 card reader was connected via PCI Express to avoid system board bottlenecks; some FireWire 800 interfaces will only connect over your PC's slower legacy PCI system bus.
The net result was that we achieved a read data rate of 45.9MB/sec off the Lexar Pro 600x card, and a write rate of 27.7MB/sec. These measurements were clearly ahead of a 300x card, but nowhere near double the performance. Lexar indicated that the results were lower than they expected and that some other reviewers had achieved. I feel that our testing represents realistic real world performance; we didn't go out of our way to optimise the test PC, or use a PC with an overclocked CPU and an OS with no applications install. We did defragment the hard drive and ensure there was a decent amount of hard disk space free, though.
Installation
With the ExpressCard test, we used a middle of the road HP laptop, with a 2GHz AMD Turion 64X2 (dual core) processor, 32 bit Windows 7 with 3GB RAM, and a 250GB 5400RPM 2.5 inch hard disk. There are faster and there are slower laptops, so we feel this represents a reasonably average specification.
ExpressCard devices can either connect via USB 2.0 or the much higher performance PCIe bus. The Lexar Pro ExpressCard CF reader is PCIe compliant, so it's performance headroom is three times greater than for FireWire 800. You'd think, therefore, that we'd see even faster transfer rates than with our previous tests using FireWire 800.
One thing that I feel could be improved is the instructions for installing the software driver. You are warned that you have to download and install the driver before using the card, but it's not clear that the ExpressCard reader needs to be mounted in its slot before the driver can be installed successfully. This is contrary to the advice for some USB devices where you need to install the driver first, and only then connect the device. If you do this with the Lexar ExpressCard, like I did, you will end up scratching your head wondering why the driver installation kept on failing.
Testing was done by copying a folder of 1GB, approximately, worth of image files. The results were interesting; for example we discovered that Lexar's own 133x card did not work at all well with the ExpressCard reader, managing well under 2MB/second transfer rates in either direction. Meanwhile, the same card used with a Lexar Pro USB 2.0 reader or a Delkin eFilm ExpressCard reader around 12MB/sec rates, not that far off the Lexar Pro 300x card in some instances.
Once again, although the Lexar Pro 600x card was clearly faster than a 300x card, it wasn't by the kind of margin indicated by the relative speed rating. And the kind of transfer speeds we saw were up to around half the speed of our tests with a desktop PC.
So how can these differences be explained? Much of it can be put down to bottlenecks in the architecture of a typical laptop computer. The main culprit is the hard disk; not only do laptop hard drives spin more slowly (typically 5400RPM compared to 7200RPM with desktop drives) but the larger diameter desktop hard drive disks mean that more data passes the read-write head on desktop hard drive in a given time than a smaller laptop disk. Basically, can read and write data to larger and faster spinning hard disk much faster than slower spinning and smaller drives.
When we used the USB 2.0 card reader, there was relatively little difference in transfer rates between any of the cards regardless of their 600x, 300x, or 133x ratings. This suggests the USB 2.0 card reader was the primary bottleneck, or perhaps the way the USB 2.0 bus connected internally. The Delkin ExpressCard reader almost certainly uses the USB 2.0 compatibility connection of the ExpressCard slot, not the direct PCIe connection, but it's clearly wired into the architecture of the laptop's motherboard more efficiently than the external USB 2.0 ports and this shows in the better transfer rates.
Finally, The 300x and 600x cards stretched ahead in ultimate transfer speed when used with the Lexar Pro PCIe connected ExpressCard. We also generally saw faster speeds for writing to the cards than for reading, which also suggests that when draw data off the cards a bottleneck occurs when the data is being written to the hard disk. There are high-performance laptops available with 7200RPM hard disks and very fast CPUs and sub-systems that will undoubtedly deliver better performance, especially with the faster cards, when using the Lexar Pro ExpressCard CF card reader.
Conclusion
The Lexar Professional ExpressCard CompactFlash card reader is a very good way to equip your laptop with a very fast reader for UDMA class CF cards, assuming that your laptop has an ExpressCard slot, which most new laptops do. It works significantly better than older ExpressCard readers that only connect via USB internally instead of PCIe like the Lexar one does. The only problem is that older CF cards (mainly slower than 233x, or ones that don't indicate they are UDMA class) don't work at all well with the Lexar ExpressCard reader. If you don't yet use UDM CF cards, this is not the card reader for you. My hunch is that a very high specification laptop will get more out of the Lexar Pro ExpressCard reader than one like we tested it on. But there is still a clear benefit over ordinary USB card readers for UDMA class CF cards. And I've seen the reader advertised for around £21, so it won't break the bank either.
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