More on Commodore Modems

From: William Levak (
Date: 2002-06-02 20:35:00

I have taken apart a number of Commodore modems to see what is inside.
The results are listed below.  

In addition to the model number, the 1660 and 1670 modems have a part
number on the bottom right of the label on the back.  In addition the 1660
modems have a name on the circuit board.

The earlier modems are made from discrete parts, standard logic chips, and
a standard modem chip (listed below).

The 1600 modem appears to be a 600 baud modem, but mine isn't working, so
I can't verify that.

The later modems use 2 80C49 microprocessors and what looks like a ROM.
Since these are custom parts, I have listed all the markings on the chips.
It looks like these were made by US Robotics.  (A 80C49 is a 8 bit
microprocessor with 128 bytes of RAM, 2K ROM, and 24 quasi bidirectional
I/O lines).

I don't have any information on the 1650 modem.  There may also be 
310476-03 and 310476-05 versions which I do not have.

If anyone wants to supply the missing information, I will add it to the
list.  The modems are held together with four pegs, one in each corner.
They are not glued and can be pried open with a screw driver.  It is
easiest to start at the edge connector.  WARNING!  I pulled the speaker
wares out while opening two of the modems, and had to solder them back.


                     Commodore Modems

    MC14412     Motorola 0-600 Baud Modem

1660   310476-01   Magic Modem TI-1660
    TMS99532    Texas Instruments 300 Baud FSK Modem

1660   310476-06   Magic Modem 1660
    MM74HC942N  National 300 Baud Modem

1670   310476-02
    U6 24 pin   USR U100
    U5 40 pin       <DKI>
                JAPAN 46067
    U4 40 pin   M80C49-206
                JAPAN 48055

1670   310476-04
    U4 28 pin   (C) USR86
                USR101 16-249
    U3 40 pin   (C)USR'85
                OKI C49-388
                JAPAN 842018
    U2 40 pin   (C)USR'85
                OKI C49-387
                JAPAN 842015
      with paper label

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