Desktop cases—and mini-tower cases under about high—are popular in business environments where space is at a premium. Currently, the most popular form factor for desktop computers is ATX, although microATX and small form factors have also become very popular for a variety of uses. In the high-end segment, the unofficial and loosely defined XL-ATX specification appeared around 2009. It extends the length of the mainboard to accommodate four graphics cards with dual-slot coolers. Some XL-ATX mainboards increase the mainboard's width as well, to allow more space for the CPU, Memory PWM, and in some cases, a second CPU socket. While the market share of these exotic high-end mainboards is very low, almost all high-end cases and many mainstream cases support XL-ATX (10 expansion slots). As of 2018, no major motherboard manufacturer has made an XL-ATX board for several years. E-ATX is similar to XL-ATX in that it is larger than ATX and is also loosely defined. Unlike XL-ATX, E-ATX motherboards and cases are still in production (as of 2020), and support quad-channel memory across 8 slots of ram, up to 4 PCI-e expansion slots for up to 4 double slot graphics cards and a single CPU such as the AMD Ryzen Threadripper 3990X. Companies like In Win Development, Shuttle Inc. and AOpen originally popularized small cases, for which FlexATX was the most common motherboard size. As of 2010 Mini ITX has widely replaced FlexATX as the most common small form factor mainboard standard. The latest mini ITX mainboards from Asus, Gigabyte, MSI, ASRock, Zotac and Foxconn offer the same feature set as full size mainboards. High-end mini ITX mainboards support standard desktop CPUs, use standard memory DIMM sockets, and mostly feature a full-size PCI-E 16× slot with support for the fastest graphics cards, although some instead use a PCI, or PCIe slot of fewer than 16 lanes. This allows customers to build a fully-fledged high-end computer in a significantly smaller case. Apple Inc. has also produced the Mac Mini computer, which is similar in size to a standard CD-ROM drive, and many manufacturers offer mini-ITX cases of similar size for low-wattage CPUs with integrated graphics. Tower cases are often categorized as mini-tower, midi-tower, mid-tower, or full-tower. The terms are subjective and inconsistently defined by different manufacturers. Full tower cases are typically or more in height and intended to stand on the floor. They can have anywhere from six to ten