The HP 840 G1 and G2 are both laptop models that were produced by Hewlett-Packard (HP). They were designed for business users and were released in 2013 and 2014, respectively.

In terms of processor power, the 840 G1 was available with a range of Intel Core processors, including the i5-4300U, i5-4200U, and i7-4600U. The 840 G2 was also available with a range of Intel Core processors, including the i5-5200U, i5-5300U, and i7-5600U. The later generation processors in the 840 G2 generally offer slightly better performance than those in the 840 G1.

In terms of upgradability, both the 840 G1 and G2 have user-upgradable RAM and storage. The 840 G1/g2 have two RAM slots. Both models can support up to 16GB of RAM. Both models also have a single 2.5-inch SATA hard drive bay, which can be used to install a solid-state drive (SSD) or a hard drive.

In terms of size, the 840 G1 and G2 are similar in terms of dimensions. Both models have a thickness of around 20mm and weigh around 1.58kg. The 840 G1 has a 14-inch display, while the 840 G2 has a 15.6-inch display.

Overall, the 840 G2 offers slightly better performance and upgradability than the 840 G1, but both models are suitable for business users who need a reliable and powerful laptop.