Combo Plus                                          AST Part Number 03-01140

The Combo Plus is a multi-function memory expansion board designed for use
with the IBM PC , XT , and 100% compatibles running at 4.77 MHz.  In it's
standard cofiguration, it comes with anywhere between 64K and 256K of RAM
using industry standard 64K dynamic RAM chips; a Clock/Calander; and a serial
port configurable as COM1: or COM2.  Options include a parallel port
configurable as LPT1: or LPT2:.  All memory installed on the Combo Plus is
designed to expand a PC to it's 640K maximum.  It does not support Extended or
EMS/EEMS type memory.  The Combo Plus is rated for use with 200ns speed RAM,
and may not work properly with faster memory.


SWITCH SETTINGS

    STARTING ADDRESS

                  SW1  SW2  SW3  SW4  SW5  SW6  SW7
                  ---  ---  ---  ---  ---  ---  ---
         64K       ON   ON   ON  OFF  OFF  OFF  OFF
        128K       ON   ON  OFF   ON  OFF  OFF  OFF
        192K       ON   ON  OFF  OFF  OFF  OFF  OFF
        256K       ON  OFF   ON   ON  OFF  OFF  OFF
        320K       ON  OFF   ON  OFF  OFF  OFF  OFF
        384K       ON  OFF  OFF   ON  OFF  OFF  OFF
        448K       ON  OFF  OFF  OFF  OFF  OFF   ON
        512K      OFF   ON   ON   ON  OFF   ON   ON
        576K      OFF   ON   ON  OFF   ON   ON   ON


        SW8 - PARITY ENABLE (Recommend on at all times)


JUMPER SETTINGS

    PORT ENABLE JUMPER BLOCK

        P2 - Short to enable parallel as LPT2: (278)
        P1 - Short to enable parallel as LPT1: (378)
        C2 - Short to enable serial as COM2:   (2F8)
        C1 - Short to enable serial as COM1:   (3F8)

    IRQ ENABLE JUMPER BLOCK

         2 - Not used, leave open
         3 - Not used, leave open
        3A - IRQ 3 short in combination with C2 for COM2:
        4A - IRQ 4 short in combination with C1 for COM1:
         4 - Not used, leave open
         5 - Not used, leave open
         7 - Not used, leave open

        Pins at location J2 are for the parallel port cable


DISABLING THE CLOCK/CALENDER

    Remove chip at location U32 (the clock chip) and cut the
    trace at pin #12, chip location U52.


SWITCH BLOCK AND JUMPER LOCATIONS

    +---------------------------------------------------------------+
    |                                                               | +---
    |                        BATT                    PORT ENABLE    +-+
    |                                                JUMPER BLOCK   | |
    |                                                        ****   | |
    |                                             +--+              | |
    |                                             |  |SW1           | |
    |                                             |  |              | |
    |                                             +--+              | |
    |                                                               | |
    |                              IRQ JUMPER BLOCK ********        +-+
    +---------------------------------------------+            +----+ |
                                                  +------------+      |
          BATT = BATTERY                                              |