Editing IBM PCjr (section)

=== Cartridges ===
The front of the PCjr exposes a pair of cartridge slots in which the user can insert software on ROM cartridges, as was common with other home computers.  Each cartridge can contain up to 64 KB of ROM.<ref name=PCjrTechRef>PCjr Technical Reference, IBM Corporation</ref>  When a ROM cartridge is inserted, the machine can automatically restart and boot off of the ROM, without requiring the user to manually reboot.  This auto-restart function is an optional feature of each cartridge: a cartridge can either restart the machine or not when it is inserted, depending on the construction of the cartridge.<ref name=PCjrTechRef/>  PCjr cartridges are strictly read-only, unlike the software cartridges of some other contemporary computers and game consoles which can also be equipped with read/write memory (RAM) or I/O hardware in a straightforward way.<ref>Examples of such other machines are the Commodore 64 and the Atari 2600 (a/k/a VCS), and all or almost all later cartridge-based game consoles.</ref>

Cartridges can also replace the system BIOS and other firmware.<ref name="norton19840320">{{cite news|author=Norton, Peter|date=March 20, 1984|title=Unearthing The PCjr's Secrets|pages=111|work=PC Magazine|url=https://books.google.com/books?id=1tFFnOMCvv4C&pg=PA111|access-date=October 24, 2013}}</ref> A number of patches from various vendors are included on a single "combo-cartridge", licensed and sold by PC Enterprises, to support add-on hardware, bypass certain limitations of design, and keep up with changing OS requirements.