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 email@example.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!