| Sign in: |
| Members log in here with your user name and password to access the your admin page and other special features. |
|
|
|
|
|| SportsShooter.com: Member Message Board
SanDisk CF card reader; NOT USB 2.0.
Phil Hawkins, Photographer
 |
Fresno | ca | usa | Posted: 10:21 PM on 03.28.11 |
->> I bought two brand-new 8-gig SanDisk UDMA cards advertising 60MB/s download speeds (the USB 2.0 spec) along with a SanDisk all-in-one reader. The download speed of my new reader advertises "up to 34MB/s transfer speeds". After much experimentation, the MAX speed I can see is 22-24 MB/s, and going through a USB 2.0 hub, drops to 12 to 14.
The highest speed is reachable only by connecting direct to my Dell laptop, Windows 7, 18-month old machine w/ USB 2.0 ports. Given that everything in the chain is rated minimum 34MB/s, where is my bottleneck? I am a tickler for getting products to perform as advertised. Yes, the new rig is faster, but I purchase 32 to 60MB/s products, and am only seeing MAXIMUM 24 MB/s speeds, and very frequently slower speeds.
How does this false advertising go down without a fight? Am I missing something? Doing something wrong? |
|
Sam Santilli, Photographer, Photo Editor
 |
Philippi | WV | USA | Posted: 8:39 AM on 03.29.11 |
| ->> Have you called ScanDisk? |
|
Eric Canha, Photographer
|
Brockton | MA | United States | Posted: 9:05 AM on 03.29.11 |
->> Phil what else is connected to your USB ports? My understanding is that USB divvies up the bandwidth of the controller for all of the devices connected whether or not they are using it. This is different from Firewire in that FW goes down the chain giving each device 100% of the bandwith for the i/o cycle assigned to it. So if you have 3 FW devices connected and 2 aren't doing anything they don't eat any bandwith.
With USB if you have a mouse or a scanner or speakers connected to the same USB controller then the OS will set aside the bandwith for those devices even if they aren't actively being used. HUBS are worse because the OS will split the bandwidth for each of the ports whether or not anything is plugged into them.
Most motherboards have 2 USB controllers. You'd have to go into the devise manager and see where the card reader is connecting and see what else is on that controller. From there you can plug the reader into the different ports until you find out which ports are connected to which controllers.
Other possibilites that would slow things down are HD speed, realtime virus detection, and any active indexing that Windows may be doing. |
|
Daniel Malmberg, Photographer
|
Huskvarna | Sweden | Sweden | Posted: 10:18 AM on 03.29.11 |
->> The theoretical max speed of USB 2.0 is 480 Mbps (Megabit per second) or 60 MB/s (MegaByte per second).
The problem is that this is only theoretical.
With some readers the controller chip in the reader slows down the speed even more.
In order to get full reading speed your reader needs to support UDMA.
The fastest USB 2.0 reader i ever heard of is a Lexar. That is no longer available on the market.
(Lexar UDMA Dual-Slot).
Which in real use supports up to 35,7 MB/s.
In order to get full read speed to your computer you should go for a FireWire 800 reader or a ExpressCard Reader.
Some tests about cards, readers and real speed can be found here:
http://www.robgalbraith.com/bins/reader_report_multi_page.asp?cid=6007-9392
Hope this helps. |
|
Erik Markov, Photographer
|
anywhere | IN | | Posted: 10:35 AM on 03.29.11 |
| ->> in the readers I've got I've found results closer to what Daniel mentioned with firewire and expresscard. Tho I will say, I think I've got the same reader as what Phil mentioned. Tho I'm using mine with cards that are rated for 30mb/s (don't have anything faster) and I pretty consistently get that 25-30mb/s. I wonder if there is something with cards above that speed that they can't achieve faster speeds even if you optimized your usb connections etc. Maybe because they are newer? I don't know. |
|
Doug Pizac, Photographer
|
Sandy | UT | USA | Posted: 11:03 AM on 03.29.11 |
->> USB ports in laptops are funneled through one controller/bus port inside. I found this out by insisting on talking to an English speaking tech person at my laptop's manufacturer. (Those in India had no clue.) I wanted a definitive answer as I was looking at using multiple card readers hooked to different USB 2.0 ports.
The example given me was let's say I have four open USB ports and the maximum bus speed is 100mb/s. If I plug in one reader, it will ingest at 100; two at 50 each; four at 25 each. But if I have a mouse or some other USB device also plugged in, they take a piece of the speed too. Thus the slow down.
My solution was to get an ExpressCard reader which is on its own separate controller/bus, and if I need to use a second reader then I plug in a USB device since it will go through a separate controller/bus. But even then, they still bottleneck simply because they are both writing to the same hard drive. And when that happens I see a noticeable drop in speed for both.
So now I've bitten the bullet and bought some Hoodman 675x speed cards and run them one at time through the ExpressCard reader. They fly. |
|
Daniel Malmberg, Photographer
|
Huskvarna | Sweden | Sweden | Posted: 11:09 AM on 03.29.11 |
->> The fastest CF-cards use a technology called UDMA (Ultra DMA).
UDMA comes in different "modes".
Different modes support different maximal transfer speeds.
More about UDMA modes and speeds here:
http://www.pcguide.com/ref/hdd/if/ide/modesUDMA-c.html
Some USB 2.0 readers don't support UDMA at all.
Other supports different UDMA modes.
(Same goes for FW and Expresscard readers).
So speed can differ a lot between different readers, even if they are using the same interface. |
|
Eric Canha, Photographer
|
Brockton | MA | United States | Posted: 11:34 AM on 03.29.11 |
| ->> One warning about Expresscard readers, there are 2 flavors being manufactured. Some connect directly to the PCI bus while others use their own internal USB controller and connect to the OS as a USB device. My Lexar Expresscard (PCI bus)reader is tops in my Vista laptop. It however consistently crashes my wife's Win7 laptop. |
|
Doug Pizac, Photographer
|
Sandy | UT | USA | Posted: 1:28 PM on 03.29.11 |
->> Eric...
Interesting difference. I have a Lexar ExpressCard reader and it works great in my Win7 64-bit Pro laptop. |
|
Eric Canha, Photographer
|
Brockton | MA | United States | Posted: 1:30 PM on 03.29.11 |
| ->> Doug do you know what version of the driver you are using. I'll have to look at her machine again. I just bought her a new USB reader to get her by. |
|
Phil Hawkins, Photographer
|
Fresno | ca | usa | Posted: 5:11 PM on 03.29.11 |
| ->> You guys are awesome! What a wealth of information I didn't know on this subject. Thanks so much. I rearranged the inputs on my computer and what a difference a new port makes, but I'm still buying the Lexar ExpressCard reader. |
|
Doug Pizac, Photographer
|
Sandy | UT | USA | Posted: 7:22 PM on 03.29.11 |
->> Eric...
I'm using whatever driver was the latest when I updated last November. |
|
Return to --> Message Board Main Index
|