Leslie Ayling wrote: > Hi all, > > Just a quick question about the different varieties of Apple 2c's. > > Not counting the 2cplus, what are the *physical* differences in > the various 2c machines between those that support the UNIDISK, > and those that don't? I'm aware of three major versions of the IIc logic board, and four firmware versions. The firmware version number is obtained via the PRINT PEEK(64447) command in BASIC, but it isn't easy to distinguish between the first two versions of the logic board without opening up the machine. The original firmware (PEEK(64447)=255) uses a 16 KB ROM and does not support the UniDisk 3.5. The original logic board was designed to support either a 16 KB or 32 KB ROM (using bank switching), with 16 KB being the default setting. To install a later firmware revision (all 32 KB), you need to do two modifications, which are at marked locations: cut a tie, and solder a blob. The only major difference on the second version of the logic board is that they changed the way in which the serial port clock is generated. On the original logic board, the serial port clock is derived from the master system clock, and the resulting frequency (1.7897725 MHz) isn't quite right, resulting in baud rates which are about 3% lower than they should be (e.g. 9600 bps on the original IIc is actually 9321 bps). This can cause communication problems with some devices that cannot handle such a large discrepancy. On the second version of the logic board, the serial port clock is derived from a 1.8432 MHz crystal oscillator, which gives the correct baud rates. They might have also changed the default setting for the ROM size, but I doubt it, as this version of the logic board can be used with the original firmware. The second version of the firmware (PEEK(64447)=0) added support for the UniDisk 3.5. As noted above, it is a 32 KB ROM, and requires a modification to the first (and possibly second) version of the logic board. The third version of the firmware (PEEK(64447)=3) added support for the memory expansion slot, which appeared in the third version of the logic board (presumably released at the same time). I'm not aware of any other significant changes on this logic board, but I expect that the default ROM size was changed to 32 KB. The fourth version of the firmware (PEEK(64447)=4) had bug fixes. > Is it simply a ROM upgrade to support the UNIDISK 3.5, or are there > some other hardware differences involved? The ROM upgrade (with cut-and-solder modifications) is all that is required to support a UniDisk 3.5 on the original IIc logic board. > Has anyone managed to get the Apple3.5 drive (from a GS for example) > working on the 2c with an appropriate driver? This is not possible. The Apple 3.5 Drive requires the SmartPort interface to operate in a faster mode (2 microseconds per bit cell instead of 4 microseconds), which is too fast for a 1 MHz 6502 or 65C02 to handle without special hardware support. In theory, it might be achievable with an acelerator, but there are several other pieces of the puzzle missing in the case of the IIc (additional control signals are required, there is no firmware support, and there isn't any system-owned RAM which can be used for translation buffers). The IIgs (2.8 MHz 65816) is fast enough to support the Apple 3.5 Drive, as is the SuperDrive card (4 MHz 65C02, I think). In both cases, there is enough RAM available. The Apple IIc+ is the only other Apple II which directly supports the Apple 3.5 Drive. It has special hardware support which eliminates the need for the extra RAM and deals with the speed issue, and the firmware includes the necessary drivers. (It also has the equivalent of a 4 MHz Zip Chip built in, but this wasn't necessary for supporting the Apple 3.5 Drive given the special hardware.) -- David Empson dempson@actrix.gen.nz Leslie Ayling schrieb in Nachricht <3c3eeb18@news.rivernet.com.au>... >Hi all, > >Just a quick question about the different varieties of Apple 2c's. Apple II Technical Notes ____________________________________________________________________________ _ Developer Technical Support Apple IIc #7: Existing Versions Revised by: Matt Deatherage November 1988 Written by: Guillermo Ortiz November 1987 This Technical Note describes the main differences between the five different IIc ROM versions which encompass the original IIc and four revisions. ____________________________________________________________________________ _ Original IIc ( $FBBF = $FF ) o Can use the IIc external drive only o No AppleTalk firmware o PR#7 boots the second drive o Mouse firmware maps to slot 4 o Serial firmware does not mask incoming linefeed characters o Serial firmware does not support XON/XOFF protocol 3.5 ROM IIc ( $FBBF = $00 ) o Can use the IIc external drive and the UniDisk 3.5 drive o AppleTalk firmware maps to slot 7 o PR#7 returns the message "AppleTalk Off Line" o Mouse firmware maps to slot 4 o Serial firmware defaults to mask all incoming linefeed characters o Serial firmware supports XON/XOFF protocol Original "Memory-Expandable" IIc ( $FBBF = $03 ) o Can use the IIc external drive, the UniDisk 3.5 drive, and the IIc Memory Expansion Card o Mouse firmware maps to slot 7 o No AppleTalk firmware o PR#7 kills the system o Serial firmware defaults to mask all incoming linefeed characters o Serial firmware supports XON/XOFF protocol Revised "Memory-Expandable" IIc ( $FBBF = $04 ) Same as Original Memory-Expandable, plus: o Keyboard buffering firmware bug fixed o Firmware returns correct information when the Memory Expansion Card is not present Apple IIc Plus ( $FBBF = $05 ) o Can use the external IIc drive, the UniDisk 3.5 drive, the Apple 3.5 drives, but not the original IIc Memory Expansion Card. o Contains a Memory Expansion Card connector o 3.5" internal drive replaces 5.25" internal drive o Mouse maps to slot 7 o PR#7 kills the system o 4 MHz 65C02 microprocessor o Accelerator chip and static RAM cache permit operation up to 4 MHz o Keyboard replaced with Apple Standard Keyboard (minus numeric keypad) o Internal power supply o Internal modem connector o Serial ports refitted with mini-DIN 8 connectors o Headphone jack has been removed o Volume control relocated above the keyboard o 40/80 column switch replaced by keyboard (Sholes/Dvorak) switch Further Reference ____________________________________________________________________________ _ o Apple IIc Technical Reference Manual, Second Edition o Apple IIc Technical Note #5, Memory Expansion on the Apple IIc o Apple IIc Technical Note #6, Buffering Blues o Apple II Miscellaneous Technical Note #2, Apple II Family Identification Routines 2.1 o Apple II Miscellaneous Technical Note #7, Apple II Family Identification o Apple II Miscellaneous Technical Note #8, Pascal 1.1 Firmware Protocol ID Bytes