
The following is from the Zenith service modules for the Z150/Z160 computers.

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CPU BOARD CONFIGURATION

For instructions on removing the card from the computer, refer to the Base Unit
Service Module.

DUAL INLINE PACKAGE SWITCHES

Two dual inline package (DIP) switches, each containing eight individual switch
sections, are used to select specific operation modes.  Switch SW1 selects the
I/O options and can be configured to select the number of 5.25-inch drive,
columns in the display, base memory size, and tells the CPU if the optional
8087 coprocessor is installed.

Switch SW2 selects the extended options and may be configured to select 50 or
60 Hz line frequency for the video display, manual or auto-boot of the disk
drives, and informs the CPU of the presence of add-on memory.

The setting of these switches is read by the CPU as either a logic zero (switch
section in the closed "ON" position), or a logic one (switch section in the
open "OFF" position).  Figure 2.1 identifies and illustrates the physical
configuration of both DIP switches SW1 and SW2.  The configuration of the DIP
switches is described in Tables 2.1 through 2.3.

                  SW1                                      SW2
+------------------------------------+   +------------------------------------+
| ON                                 |   | ON                                 |
| ^ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+  |   | ^ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+  |
| | | | |*| | | | | | | |*| |*| |*|  |   | | |*| | | |*| |*| |*| | | | | |*|  |
| | | | | | | | | | | | | | | | | |  |   | | | | | | | | | | | | | | | | | |  |
| | |*| | | |*| |*| |*| | | | | | |  |   | | | | |*| | | | | | | |*| |*| | |  |
| | +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+  |   | | +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+  |
|    0   1   2   3   4   5   6   7   |   |    0   1   2   3   4   5   6   7   |
+------------------------------------+   +------------------------------------+

                            Figure 2.1.  DIP Switches

Table 2.1.  SW1 DIP Switch Configuration
------------------------------------------------------------------------------
Switch
Section   Function              SWITCH SETTINGS
------------------------------------------------------------------------------
0         Floppy Disks          ON:  No Floppy Drives Attached
          Attached              OFF:  Floppy Drives are Attached

1         8087 Installed        ON:  Not Installed
                                OFF:  8087 Installed

2 and 3   Base Memory Size      OFF, OFF:  64K
                                NOTE:  Sections 2 and 3 are always set to this
                                       position.

4 and 5   Column Display        ON, ON:  Reserved
          Type                  OFF, ON:  40 X 25
                                ON, OFF:  80 X 25
                                OFF, OFF:  Monochrome Video

6 and 7   Number of 5.25-inch   ON, ON:  1 Drive
          Drives Installed      OFF, ON:  2 Drives
                                ON, OFF:  3 Drives
                                OFF, OFF:  4 Drives
------------------------------------------------------------------------------



Table 2.2.  SW2 DIP Switch Configuration
------------------------------------------------------------------------------
Switch
Section   Function              SWITCH SETTINGS
------------------------------------------------------------------------------
0, 1, 2,  Add-On Memory Size    The DIP switches are configured to accommodate
3 and 4                         the various CPU memory capacities as required
                                for each computer model.  (See Table 2.3.)

5 and 6   Select Boot Mode      ON, ON:  Manual Boot
          and Booted Drive      OFF, ON:  Autoboot Floppy
                                ON, OFF:  Autoboot Winchester
                                OFF, OFF:  Manual Boot

7         Line Frequency        ON:  60 Hz Display
          Select for CRT        OFF:  50 Hz Display*
          Screen Sweep

*Not Recommended
------------------------------------------------------------------------------



Table 2.3.  SW2 Memory Size Switch Section Settings
---------------------------------------------------
0     1     2     3     4         NUMBER OF BYTES
---------------------------------------------------
ON    ON    ON    ON    ON     =         64K
ON    OFF   ON    ON    ON     =        128K
ON    ON    OFF   ON    ON     =        192K
ON    OFF   OFF   ON    ON     =        256K
ON    ON    ON    OFF   ON     =        320K
ON    OFF   ON    OFF   ON     =        384K
ON    ON    OFF   OFF   ON     =        448K
ON    OFF   OFF   OFF   ON     =        512K
ON    ON    ON    ON    OFF    =        576K
ON    OFF   ON    ON    OFF    =        640K
---------------------------------------------------



JUMPER CONNECTOR CONFIGURATION

A row of jumper connectors is located in the center of the CPU card (Figure
2.2).  The jumper connectors configure the monitor ROMs.  The jumpers may be
configured as follows:

*  A jumper connected between pins 5 and 10 informs the CPU that ROM 1 is a
   256K device.

*  A jumper connected between pins 4 and 9 informs the CPU that ROM 1 is a
   128K device.

*  A jumper connected between pins 3 and 8 informs the CPU that ROM 2 is a
   256K device.

*  A jumper connected between pins 2 and 7 informs the CPU that ROM 2 is a
   128K device.

*  A jumper connected between pins 1 and 6 informs the CPU that a RAM chip is
   installed into the ROM 2 socket.  The card normally is supplied with no
   RAM installed.

                                  jumpers-----------+
                                              |     |
                     ^                        V     V
                     |                       +-+   +-+
                    top           pins---> * |*| * |*| *
                   bottom              +-> * |*| * |*| *
                     |                       +-+   +-+
                     V                         P203

                     Figure 2.2.  Jumper Connections

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MEMORY BOARD CONFIGURATION

< no switches on the memory board . . . first page repeats CPU board memory >
< switch settings . . . see above . . . . . . . . . . . . . . . . . . . . . >

CONFIGURATION JUMPERS

J401, J402, and J403 are configuration jumpers located on the memory card.
J401 is used as a card-select jumper.  If only one memory card is used, J401
should be positioned to the left away from the edge connector), marked "1st".
If the system has two memory cards, position the jumper on the card to be
designated as the first block of 320K-byte memory to "1st", and the jumper on
the card containing the second block to the right, marked "2nd".  If 256K RAM
chips, as opposed to 64K, are used, only one card is used and J401 should be
positioned to "1st".

J402 and J403 on the initial card are used to assign the parallel output port
to a desired I/O port address according to Table 2.2.

Table 2.2.  Parallel Port Address Selection
--------------------------------------------
J403     J402    CONFIGURATION          PORT
--------------------------------------------
  0        0     Parallel Printer       *3BC      NOTE:  Zenith manual doesn't
                                                         say so, but 0=OUT and
  0        1     Parallel Printer        378             1=IN.

  1        0     Port Disabled           N/A

  1        1     Port Disabled           N/A

*This port corresponds to the monochrome 
 display port on the IBM PC.
--------------------------------------------

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