When Apple launched the new iPhone 6 and iPhone 6+, both of them had a great resolution display that makes apps and games run in a better performances with a higher display rate. However, if you run an older device and wish to use iPhone 6 resolution, then you can try Upscale, that allows older devices run at a resolution of 640 x 1136 pixels, and the tweak lets you change this to any arbitrary value.
The tweak is in beta, and should be used with extreme caution, as it can cause reboot cycles, forcing you to restore your device. Upscale comes with 3 preset resolutions:
iPhone 5/5s (640 x 1136)
iPhone 6 (750 x 1334)
iPhone 6+ (1242 x 2208)
As you’ll notice, the higher resolution makes everything a little smaller on the screen, which you may or may not like depending on your choices.
In order to install it, you will have to add the following repo to your Cyida sources: repo.bd452.com and search for "upscale".. That's it.