A legacy-free PC is a type of personal computer that lacks a floppy or optical disc drive, legacy ports, and an Industry Standard Architecture (ISA) bus (or sometimes, any internal expansion bus at all). According to Microsoft, "The basic goal for these requirements is that the operating system, devices, and end users cannot detect the presence of the following: ISA slots or devices; legacy floppy disk controller (FDC); and PS/2, serial, parallel, and game ports."[1] The legacy ports are usually replaced with Universal Serial Bus (USB) ports. A USB adapter may be used if an older device must be connected to a PC lacking these ports.[2] According to the 2001 edition of Microsoft's PC System Design Guide, a legacy-free PC must be able to boot from a USB device.[3]
Removing older, usually bulkier ports and devices allows a legacy-free PC to be much more compact than earlier systems[4] and many fall into the nettop or all-in-one form factor. Netbooks and ultrabooks could also be considered a portable form of a legacy-free PC. Legacy-free PCs can be more difficult to upgrade than a traditional beige box PC, and are more typically expected to be replaced completely when they become obsolete.[5] Many legacy-free PCs include modern devices that may be used to replace ones omitted, such as a memory card reader replacing the floppy drive.
As the first decade of the 21st century progressed, the legacy-free PC went mainstream, with legacy ports removed from commonly available computer systems in all form factors. However, the PS/2 keyboard connector still retains some use, as it can offer some uses (e.g. implementation of n-key rollover) not offered by USB.[6]
With those parts becoming increasingly rare on newer computers as of the late 2010s and early 2020s, the term "legacy-free PC" itself has also become increasingly rare.