Apple II peripheral cards
The Apple II Language Card was a popular expansion card for the first home computer Apple II that could show through Bankswitching optional RAM in the ROM address space. Thus, a memory extension up to 64 kB has been made possible. The card was originally sold only in conjunction with extension languages, for example with Apple Pascal and FORTRAN Apple. Replicas of the map by other companies but were soon available without such language, and from around 1982 put many Apple applications require such a card.
Technology
The 6502 microprocessor of the Apple II had a 16- bit address space, so could of home address only 64kB memory. From this address space of the Apple II used up to 48kB of RAM, then joined 4 kB, in which I / O addresses for memory mapped I / O and the ROMs were placed on expansion cards. The upper 12 kB were for the built-in ROM of the Apple II reserved ( 10kB for the BASIC interpreter, 2 kB for the actual operating system ).
The Language Card blinded to the access to specific I / O registers instead of 12 kB of ROM in the address space. The first 4 kB by a second level of bank switching could be switched between two memory banks, so that the card total of 16 kB bot. Other manufacturers used the same principle to display additional 4KB blocks in the address space, and so to come to significantly more than 64 kB of total memory.
The card was always used by default in slot 0 (far left). It basically works in the other slots, but almost all programs, including operating systems Apple DOS and Apple ProDOS, the card offers in slot 0
The self offered by Apple Language Card additionally contained a ROM chip which was identical in content to the so-called car boot ROM of the Apple II. Thus also the Apple II original model was the ability to start when switched on without entering commands automatically an operating system or another program from a floppy disk. The replicas offered by other companies in the Language Card waived for copyright reasons on this ROM chip; on the now far more common Apple II brought this anyway no added value.
When further developed computer model Apple IIe and all later models of the series a memory expansion on the type of Language Card was already installed. For this accounted for the slot 0, so that only seven standard Apple slots (1-7) were present.