Apple IIc ROM Versions
Apple IIc ROM Versions is a two-page summary of the four Apple IIc firmware versions and the hardware changes that went with them. It was distributed by Apple2Online (the PDF is dated August 2010) and names no author. It is a community document, not an Apple publication.
Contents
[edit | edit source]- Original IIc (ROM version 255): 16 KB ROM; one external 5.25-inch drive, bootable with PR#7; serial firmware without line-feed masking or XON/XOFF; no self-test.
- Serial port timing fix: original boards made between April and November 1984 derived both serial ports' timing from a 74LS161, about 3 per cent slower than the minimum specified. Some non-Apple modems and printers at 1200 bit/s or faster misbehaved; devices at 300 bit/s and below were unaffected. Apple changed to an oscillator in production and swapped boards for owners who could show an affected device.
- UniDisk 3.5 support (ROM version 0), November 1985: ROM doubled to 32 KB; intelligent drive support; self-test; mini-assembler, STEP and TRACE; unfinished AppleTalk code ("APPLETALK OFFLINE" on PR#7); a 3.5-inch disk sticker beside the drive port on upgraded machines.
- Memory Expansion IIc (ROM version 3), September 1986: new logic board with a 34-pin memory card socket; on-board RAM reduced from sixteen 64K×1 chips to four 64K×4; RAM disk in slot 4 and mouse in slot 7; new keyboard without the rubber anti-spill mat; light grey keyboard, drive latch and power cords.
- Memory Expansion fix (ROM version 4), January 1988: better detection of installed RAM, a terminal-mode fix for the modem port and a keyboard buffering fix. Free only to owners of the memory-expansion IIc.
What this document does not contain
[edit | edit source]It gives no Apple part numbers, board numbers or model numbers and cites no sources. Apple's own account of the same changes, with the ROM part numbers (342-0445-A and -B), the model numbers A2S4000 and A2S4100 and the service procedures, is in the Apple IIc Technical Procedures (File:Apple IIc Technical Procedures.pdf).
Pages that cite this document
[edit | edit source]- Apple IIc: ROM version numbers, the 74LS161 serial timing fault and its production window, the original ROM's serial and self-test limitations
Download: Apple IIc ROM Versions.pdf