Apple //c (UniDisk 3.5) - MAME machine

Computer published 40 years ago:

Apple IIc © 1984 Apple Computer Co.

TECHNICAL
Microprocessor:

• 65C02 running at 1.023 MHz
• 8-bit data bus

Memory:
-- 128 KB RAM built-in
-- 32 KB ROM built-in (16 KB ROM in original)

• Expandable from 128 KB to 1 MB (only through non-conventional methods in original)

Video:

• 40 and 80 columns text, with 24 lines
• Low-Resolution: 40 × 48 (15 colors)
• High-Resolution: 280 × 192 (6 colors)
• Double-Low-Resolution: 80 × 48 (15 colors)
• Double-High-Resolution: 560 × 192 (15 colors)

Audio:

• Built-in speaker; 1-bit toggling
• User adjustable volume (manual dial control)

Built-in storage:

• Slim-line internal 5.25-inch floppy drive (140 KB, single-sided)

Internal connectors:

• Memory Expansion Card connector (34-pin)•

• Only available on ROM 3 motherboard and higher; original IIc: NONE

Specialized chip controllers:

• IWM (Integrated Wozniak Machine) for floppy drives
• Dual 6551 ACIA chips for serial I/O

External connectors:

• Joystick/Mouse (DE-9)
• Printer, serial-1 (DIN-5)
• Modem, serial-2 (DIN-5)
• Video Expansion Port (D-15)
• Floppy drive SmartPort (D-19)
• 12-Volt DC connector input (DIN-7, male)
• NTSC composite video output (RCA connector)
• Audio-out (?-inch mono phone jack)

TRIVIA
The Apple IIc was released on April 24, 1984 in North America during an Apple-held event called 'Apple II Forever'. The new machine was proclaimed as proof of Apple's long-term commitment to the Apple II series and its users, an assurance the company's older technology would not be forsaken or dropped with the recent introduction of the Macintosh. Beyond displaying a commitment to the vitality of the Apple II line, the IIc was also seen as the company's response to IBM's new PCjr.

While essentially an Apple IIe computer in a smaller case, it was not a successor, but rather a portable version to complement it. One Apple II machine would be sold for users who required the expandability of slots, and another for those wanting the simplicity of a plug and play machine with portability in mind.

The machine introduced Apple's Snow White design language, notable for its case styling and a modern look which soon became the standard for most Apple equipment and computers, and continued for nearly a decade after. The Apple IIc introduced a unique off-white coloring known as 'Fog', chosen to enhance the Snow White design style. The Apple IIc, along with a few other peripherals, was the only computer made by Apple to use the 'Fog' coloring.

While relatively light-weight and compact in design, the Apple IIc was not a true portable in design as it lacked a built-in battery and display.
Codenames for the machine while under development included: Lollie, ET, Yoda, Teddy, VLC, IIb, IIp.

UPDATES
The Apple IIc was in production from April 1984 to August 1988, and during this time accrued some minor changes. These modifications included three new ROM updates, a bug-fix correction to the original motherboard, a newly revised motherboard, and a slight cosmetic change to the external appearance of the machine. The ROM revision for a specific Apple IIc is determined by entering the Applesoft BASIC programming language and typing in the command PRINT PEEK (64447) which returns the value indicating the particular ROM version.

• Original IIc (ROM version 255): The initial ROM, installed in machines produced during the first year and a half of production, was 16 KB in size. The only device which could be connected to the disk port was (one) external 5.25-inch floppy drive; software could be booted from this external drive by typing the command PR#7. The serial port did not mask incoming linefeed characters or support the XON/XOFF protocol, unlike all later firmware revisions to come. There was no self-test diagnostic present in this ROM, holding down the solid-Apple key during cold boot merely cycled unusual patterns on screen which served no useful purpose or indication of the machine's health.
• Serial port timing fix: The original Apple IIc motherboard (manufactured between April and November 1984) derived the timing for its two serial ports through a 74LS161 TTL logic chip. It was later found that this method's timing was 3% slower than the minimum requirement specified and caused some third party (i.e. non-Apple) modems and printers, which operated at 1200 bits per second (baud) or faster, to function improperly. Slower serial devices operating at 300 baud or less were unaffected, as well as some faster devices which could tolerate the deviation. The solution to ensure all devices were compatible was to replace the TTL chip with an oscillator during manufacture. Apple would swap affected motherboards for users who could prove they had an incompatible serial device (e.g. a third-party 1200-baud modem which presented problems; not all did). It is important to note the problem did not affect all owners; it was more or less a hit-or-miss issue depending on the specific device connected.
• UniDisk 3.5 support (ROM version 0): This update, introduced in November 1985, came in the form of an upgrade to the ROM firmware which doubled in size from 16 KB to 32 KB. The new ROM supported intelligent devices such as the Apple UniDisk 3.5-inch (800 KB) floppy drive, in addition to an external 5.25-inch floppy drive. A new self-test diagnostic was provided for testing built-in RAM and other signs of logic faults. The Mini-Assembler, absent since the days of the Apple II Plus, made a return, and new Monitor Step and Trace commands were added as well. The upgraded ROM added rudimentary support for an external AppleTalk networking device which was yet to be developed. When attempting to boot virtual slot 7, users would encounter the message APPLETALK OFFLINE. The IIc, however, had no built-in networking capabilities, and no external device was ever released. The upgrade consisted of a single chip swap (and a trivial motherboard modification), which Apple provided free only to persons who purchased a UniDisk 3.5 drive. A small sticker with an icon of a 3.5-inch floppy diskette was placed next to the existing 5.25-inch diskette icon above the floppy drive port indicating the machine had been upgraded.
• Memory Expansion IIc (ROM version 3): Introduced in September 1986 simultaneously with the Apple IIGS, this model introduced a new motherboard, new keyboard and new color scheme. The original Apple IIc had no expansion options and required third-party cards to perform various hardware tricks. This could be done by removing the CPU and MMU chips and squeezing a special board into these sockets, which then used bank switching to expand memory (RAM). This was similar to the function of the auxiliary slot in the original Apple IIe. The new motherboard added a 34-pin socket for plugging in memory cards directly, which allowed for the addressing of up to 1 megabyte (MB) of memory using Slinky-type memory cards. The onboard chip count was reduced from 16 memory chips (64K×1) to four (64K×4). The new firmware removed the code for the cancelled AppleTalk networking device and replaced it with support for memory cards. Bumping out the non-supported AppleTalk functionality, memory now lived in virtual slot 4, and mouse support moved to slot 7. The new keyboard no longer had the rubber anti-spill mat and offered generally more tactile and responsive keys that felt more clicky. At the same time, the color of the keyboard, floppy drive latch, and power supply cords changed from beige to light grey, which matched the new Platinum color scheme of the Apple IIGS. The case style, however, remained Snow White. Owners of the previous IIc model were entitled to a free motherboard upgrade if they purchased one of Apple’s IIc memory expansion boards (they did not receive the new keyboard or the cosmetic changes).
• Memory Expansion fix (ROM version 4): In January 1988, a new ROM firmware update was issued to address bugs in the new memory expandable IIc. Changes included better detection of installed RAM chips, correction of a problem when using the serial modem port in terminal-mode, and a bug fix for keyboard buffering. The ROM upgrade was available free of charge only to owners of the memory expansion IIc. This was the final change to the Apple IIc until superseded by the Apple IIc Plus (identified as ROM version 5).
• International versions: Like the Apple IIe before it, the Apple IIc keyboard differed depending on what region of the world it was sold in. Sometimes the differences were very minor, such as extra local language characters and symbols printed on certain keycaps (e.g. French accented characters on Canadian IIc, or the British Pound symbol on the UK IIc) while other times the layout and shape of keys greatly differed (e.g. European IIc). In order to access the local character set, the Keyboard switch above the keyboard was depressed, which would instantly switch text video from the US character set to the local set. The DVORAK keyboard layout was not available on international IIcs—the feature had been intended to switch between international keyboards; the DVORAK layout was merely added to give the switch a function on US IIcs. In some countries these localized IIcs also supported 50Hz PAL video and the different 220/240-volt power of that region by means of a different external power supply — this was a very simple change, since the IIc had an internal 12-volt power converter. The international versions replaced any English wording printed on the case (specifically the keyboard toggle switch, Power and Disk Use drive activity labels) with graphical icon symbols that could be universally understood.

CONTRIBUTE
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