Re: RE:3.5" UniDisk on a IIc

[tomk@pro-nsdapple.cts.com (Tom Kelly)]

In <43.48565992.Logic.IS@logicbbs.org> Jim.Low@logicbbs.org writes:

>I don't know about Apple in the USA, but as of April 15, Apple Canada has 
>discontinued the free Apple IIc motherboard swap for early IIc's so they 
>would support the Unidisk.
> 
 
The original ROM is 128K
P/N        (342-0272-A)
Print Peek(64447) = 255
 
The upgraded ROM (UniDisk) is 256K
P/N        (342-0445)
Print Peek(64447) = 0
 
I have several  Apple IIc computers, some are already upgraded.
I have a EPROM programmer, so I copied the upgraded ROM into a EPROM.
Then I removed the original ROM from the socket and installed the EPROM
in its place.
 
Since the original ROM was 128K, but the upgraded ROM is 256K,
I had to "modify" the motherboard as noted below.
"bowtie" W1    (open)
"bowtie" W2    (shorted)

 To find out which //c ROM version you have, go into BASIC (or if you
 don't have a disk handy, just turn on the computer and hit ctrl-reset
 after you see the "Check disk drive." message) and type the following
 line and hit return at the "]" prompt:
 
 PRINT PEEK (64447)
 
 
 Values of the PEEK (64447) are as follows:
 
 255   Original //c ROM                   (Can't use UniDisk 3.5")
   0   3.5 ROM //c                        (CAN use UniDisk 3.5")
   3   Original "Memory-expandable" //c   (CAN use UniDisk 3.5")
   4   Revised "Memory-expandable" //c    (CAN use UniDisk 3.5")
 
   5   Apple //c+  (built-in 3.5" drive; can use Unidisk 3.5" AND Apple 3.5")
 
 For those of you who might be interested in other differences between
 //c ROM versions, see Apple // Tech Note #7 for the Apple //c.
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