Catleap 2B Underclock

[kevinsbane]

So, I've got a Catleap 2B that I've been planning on replacing with a Qnix (since it works better for me). Now, I find that running the Qnix alongside the Catleap is almost redundant - I simply don't need the extra space. So I'm trying to figure out how to run the Catleap off my laptop.

Now, as I understand, ToastyX has managed to run a Catleap at up to 60hz via HDMI -> SL-DVI adapter. I have no illusions that my laptop can possibly do a full 1440p at 60hz, and nor do I need it - it would be for CAD work which doesn't need perfect refresh rates.

Here's what I want to do:
I want to connect my Laptop (Lenovo Thinkpad X220 - Sandy Bridge, Intel HD 3000 graphics, VGA port and DP++) to my Catleap using a DisplayPort -> SL-DVI (passive) adapter, running it at full resolution but reduced refresh rate (42hz? 30hz? whatever). As I understand, passive DP->SL-DVI adapters are simply pass-throughs and contain no graphics logic.

Intel provides a handy little "custom resolution" page in their software, but it does not seem to want to let me input a custom resolution. I tried 2560x1440@30hz/42hx, but it says that the monitor does not support that mode (when I know it can be done, since ToastyX has done it). What am I missing here? Is there any way to, say, edit my monitor driver file to enable or force my laptop to recognize 2560x1440@30hz as its preferred resolution?