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From: acliu@skat.usc.edu (Alex C. Liu)
Newsgroups: comp.sys.cbm
Subject: Second Sid Chip Alternative?
Message-ID: <22796@usc.edu>
Date: 10 Feb 90 03:53:41 GMT
Sender: news@usc.edu
Organization: Maze Inc.
Lines: 40

Hello,
   I always wanted to add a 2nd SID chip to my computer but didn't
wanted to surrender the ONLY cart port of the C128 or ONE of the TWO
I/O lines for the C128.  Now, I am asking, is it possible to remove
the Sid chip from the C128 mother board, and replace it with a small
PC board but with 2 Sid chips and using the logic bellow as Chip
Select.  Now, before spending the $$ on this sort of stuff, I was
wondering it this is actually possible?  (I know I would have to patch
StereoSidPlayer to access the right SID chip, since it would be mapped
in a different address)  I want to know this, 'cos, I don't want to
expend lots of time in a project that will take my C128D to the Repair
Shop...
              _    ___
D   , A   , R/W,0 ,RES       /* Standard Pins that come */
 7-0   4-0       2           /* from CPU to SID Chip    */
---+--------------------+
   |                    |
   |      __________    |      __________ 
   |     |          |   |     |          |
   +-----|          |   +-----|          |
         |          |         |          |
         |   SID1   |         |   SID2   |
         |    __    |         |    __    |
         |____CS____|         |____CS____|
              |                    |
             _|_                  _|_
            / OR\                / OR\
           |_---_|              |_---_|
             | |                  | |
             | o                  | |   /* Standard CS to  */
             |/_\                 | |   /* select SID Chip */
__           | |                  | |
CS-----------+-(------------------+ |
               |                    |   /* A(5) line from Address */
A -------------+--------------------+   /* bus (added for this)   */
 5
______________________________________________________________________
Alex C. Liu                   | INTERNET: acliu%skat@usc.edu
Voice: (213) 749-2730         | BITNET: acliu%skat@gamera
Q-Link: Alejandro             | UUCP: ...!usc!edu