Why does my UGA-2K-A USB 2.0 graphics adapter only output 1280 x 720 resolution on my 27" Apple LED Cinema Display?


#1

!](https://sslproxy.getsatisfaction.com/sslproxy/SWhAdDNLMG5zdGFuVGlWenmLbJDGd3CABhjZermgcystANA4T6nd0pzV0fSzBRRGOd17A4b8ZLwi6-HESbXI0qCyZ266mQDWgCudRtb_bR8ApuW4fQteq054CzfEeZ-3pN5JFQ_8HIIKopEXmU69fGQzQVZ5miau_TGCr9juyU28CS2UIHQ71CQdLOQqsNjE.jpg)](http://s3.amazonaws.com/satisfaction-production/s3_images/325676/Screen_shot_2010-11-03_at_9.52.26_AM.jpg)I understand that model UGA-2K-A USB graphics adapter with DL195 chip supports up to 2048 x 1152 resolution.

When connecting to a 27" Apple LED Cinema Display (which supports 2048x1152, http://www.apple.com/displays/specs.html) through the Atlona AT-DP400 (which also supports 2048x1152, http://www.atlona.com/Atlona-Dual-Lin…), and using the latest 1.6b3 Displaylink driver for Mac OSX, the max resolution I can get is only 1280x720.

The attached screenshot shows my Main Display (first 27" LED Cinema Display directly connected to Macbook Pro via miniDisplayport), Display 2 (Macbook Pro display), and Display 3 (second 27" LED Cinema Display connected via UGA-2K-A and Atlona AT-DP400).


#2

Hi Ray,

Thanks so much for your question and thanks for posting the screenshot and background to research it!

Unfortunately, you are not alone in hitting this problem of a single mode offered on the Cinema display. It appears this is a fundamental limitation of the Cinema display.

Here is the Apple KB article explaining why their product has this limitation on all standard single-link DVI connections: http://support.apple.com/kb/HT3571

Here’s what I believe is happening:

Apple has made the Cinema HD display more cost-effective by only supporting two modes in the display itself: 2560x1600x24@60 and the 1/4 mode of 1280x800x24@60. Only these two modes reported in the monitor’s capabilities (EDID) and sent back to the attached graphics card. Unfortunately, the 2560 mode is higher than any USB graphics chip supports, so when connected through any single-link DVI connection or USB connection, 1280x800 is the only mode offered.

So then why are other modes in-between able to be offered, when the Cinema display is connected directly to a Mac? Apple apparently uses the system’s GPU to do real-time full screen scaling to offer those other modes. They’ve been able to shift the cost of having a hardware scaler away from the display, and just reuse the systems’ GPU when directly connected to a Mac GPU.

But the DisplayLink drivers (being a software GPU) don’t offer that scaling today, and it’s not clear to me if the performance would be acceptable if they do in the future. But, regardless, they are looking at the feature for a future release.

See http://displaylink.org/forum/showthre… from the DisplayLink support forums for a user of a Sewell hitting the same thing.

So unfortunately, this is a somewhat fundamental limitation, with an uncertain long-term workaround.

We don’t ever want buyers stuck with hardware that isn’t doing what they need, even if it’s a limitation of another component. So a return is no problem. Just visit http://www.amazon.com/gp/css/returns/… or if you’re past 30 days, we’d be happy to process a return directly if you email your amazon order id to support@plugable.com

We’re sorry there was no easy solution here. But thank you for posting, so the limitations here are more clear to others in the future!

Thank you!
Bernie


#3

Hi Bernie

Will the UGA-2K-A support 2560 x1080…Ive been scratching my head about this issus and have not found a solution on the web, much advice is appreciated !](https://d2r1vs3d9006ap.cloudfront.net/s3_images/1080041/screen_inline.jpg?1406158380)](https://d2r1vs3d9006ap.cloudfront.net/s3_images/1080041/screen.jpg?1406158380)


#4

Hi Derrick,  

Thanks for asking! The max resolution of the UGA-2K-A is 2048x1152, so it’s not capable of the 2560x1080 mode you’re looking for.   When Windows chooses a mode (or offers modes), it is showing the common modes that are supported by *both* the graphics adapter and the monitor, so you’re presented with valid modes (that won’t end up in a black screen).   

Just let us know if there are any other specific questions - we’d be happy to help.  Thanks!
Bernie


#5