Editing Apple IIc ROM Versions

<pdf> File:Apple IIc ROM Versions.pdf </pdf>

'''Apple IIc ROM Versions''' is a short community document, published via Apple2Online with no named author, covering the four [[Apple IIc]] firmware revisions and the hardware changes that accompanied them. '''It is not an Apple publication''' and is identified as a secondary source wherever this wiki cites it.

== What is in it ==
* The '''serial port timing fix'''. Original IIc motherboards "manufactured between April and November 1984" derived the timing for both serial ports through a '''74LS161''' TTL counter. That timing ran about 3 per cent slower than the specified minimum, which made some non-Apple modems and printers at 1200 bit/s or above misbehave; devices at 300 bit/s and below were unaffected. Apple replaced the TTL device with an oscillator in production, and swapped affected motherboards for owners who could show an incompatible device.
* Summaries of ROM 255 (original, 16 KB), ROM 0 (UniDisk 3.5, 32 KB, November 1985), ROM 3 (Memory Expansion, September 1986) and ROM 4 (Revised Memory Expansion, January 1988).
* The chip-count reduction on the Memory Expansion board, from sixteen 64K&times;1 devices to four 64K&times;4 devices, and the 34-pin memory card socket that board introduced.

Download: [[:File:Apple IIc ROM Versions.pdf|Apple IIc ROM Versions.pdf]]

== See also ==
* [[Apple IIc]]
* [[Apple IIc Technical Reference Manual]]

[[Category:Apple Documentation]]
[[Category:Documentation]]
[[Category:Apple Vintage Computers]]