previous MacBooks. Unlike the unibody MacBook Pros, the memory is soldered onto the logic board and is therefore not upgradable. The solid state drive is not soldered and can be replaced by users, although it has a proprietary connector and form factor. The battery is glued into place; attempts to remove it may destroy the battery and/or trackpad. The entire case uses proprietary pentalobe screws and cannot be disassembled with standard tools. While the battery is glued in, recycling companies have stated that the design is only "mildly inconvenient" and does not hamper the recycling process. The initial revision includes Intel's third-generation Core i7 processors (Ivy Bridge microarchitecture). Apple updated the line, on October 22, 2013, with Intel's Haswell processors and Iris Graphics, and 802.11ac Wi-Fi. The chassis of the 13-inch version was slightly slimmed to to match the 15-inch model. The lower-end 15-inch model only included integrated graphics while the higher-end model continued to include a discrete Nvidia graphics card in addition to integrated graphics. Support for 4K video output via HDMI was added but limited the maximum number of external displays from three to two. On March 9, 2015, the 13-inch model was updated with Intel Broadwell processors, Iris 6100 graphics, faster flash storage (based on PCIe 2.0 × 4 technology), faster RAM (upgraded from 1600MHZ to 1866MHZ), increased battery life (extended to 10 hours), and a Force Touch trackpad. On May 19, 2015, 15-inch model added Force Touch and changed the GPU to AMD Radeon R9 M370X, SSD based on PCIe 3.0 × 4 technology, the battery life was extended to 9 hours, and the rest of the configuration remained unchanged. The higher-end 15-inch model also added support for dual-cable output to displays. The 15-inch models were released with the same Intel Haswell processors and Iris Pro graphics as the 2014 models due to a delay in shipment of newer Broadwell quad-core processors. Apple continued to sell the 2015 15-inch model until July 2018. In June 2019, Apple announced a worldwide recall for certain 2015 15" MacBook Pro computers after receiving at least 26 reports of batteries becoming hot enough to produce smoke and inflict minor burns or property damage. The problem affected some 432,000 computers, mostly sold between September 2015 and February 2017. The company asked customers to stop using their computers until Apple could replace the batteries. In September 2019, India's Directorate General of Civil