The Lumia 640 XL was announced by Microsoft earlier this month at MWC 2015, being the more expensive variant of the Lumia 640. Even if it's larger and slightly better at some things (like photography), the 640 XL uses the same 1.2 GHz Snapdragon 400 processor as the 640, while also having the same amount of RAM: 1 GB. However, it looks like the Chinese version of the Lumia 640 XL brings improvements in these two departments.
According to China's Telecommunication Equipment Certification Center, which recently approved a TD-LTE version of the Lumia 640 XL, the handset comes with 2 GB of RAM, and a quad-core processor clocked at 2.2 GHz (this is definitely not a Snapdragon 400, but it's not clear what model it is). These changes should obviously make the China-bound 640 XL a superior device. The rest of its features seem to have remained unaltered, thus including a 5.7-inch 720p display, 5 MP front-facing camera, 13 MP rear camera, and 8 GB of expandable storage space.
like the Lumia 640, the 640 XL will run Windows Phone 8.1 at launch, with an update to Windows 10 coming later this year (possibly sometime in the summer).
Microsoft will release the Lumia 640 XL in April, for prices starting at around $220. We don't know if the more powerful version of the handset will be available outside of China, but we're going to let you know when we find out.
source: TENAA (translated)