[comp.sys.ibm.pc] Need help on genuine IBM PC motherboard switches

news@mfci.UUCP (Usenet) (11/17/89)

We have several IBM PC Model 5150 B's around here
and I want to persuade one of them that it has a mono monitor.

How do I set the dip switches on the motherboard for this?
(Please send info on all switch settings if you have them.)

Many thanks.

(Pre-emptive flame:  I'd RTFM but some F person stole TFM.)

brendan fagan     fagan@mfci.UUCP  or fagan@multiflow.com

unkydave@shumv1.uucp (David Bank) (11/17/89)

In article <1124@m3.mfci.UUCP> fagan@mfci.UUCP (Brendan Fagan) writes:
>
>We have several IBM PC Model 5150 B's around here
>and I want to persuade one of them that it has a mono monitor.
>
>How do I set the dip switches on the motherboard for this?
>(Please send info on all switch settings if you have them.)
>
>Many thanks.
>
>(Pre-emptive flame:  I'd RTFM but some F person stole TFM.)
>
>brendan fagan     fagan@mfci.UUCP  or fagan@multiflow.com

   All to happy to help. I'll be drawing this information directly from
the IBM "Hardware Maintenance and Service" manual for the 5150.
I'll be supplementing it with some other info I have, since my copy
of the manual insists that switch #2 on SW1 is unused, when it actuality
it is used to indicate the presence of an 8087.

   Anyway, in answer to your question, switches 5 & 6 of SW1 should be
set to "OFF" to convince the PC it has a mono monitor. No other changes
are needed.

   Now, about switch settings in general:

   SW1 (also called Switch Pack 1) is used mainly to indicate options
on the system, such as drives and coprocessors and monitors. SW2 (also
called Switch Pack 2) is used pretty much exclusively to indicate
system memory.

   The switches and their meanings for SW1 are:

       1    -  Indicates if any floppy drives are installed. If this
               switch is "ON", switches 7 & 8 are ignored. If it is
               "OFF", 7 & 8 will be decoded to determine the number
               of floppy drives
       2    -  Used to indicate the presence or absence of a math
               coprocessor (8087). When this switch is on, the 
               equipment check call will indicate there is no 8087.
               If the switch is "OFF", then the presence of a math
               coprocessor is indicated.
       3,4  -  Shows the amount of system/mother/planar board memory.
               Settings are:

                     Amount (in KB)       Switch 3    Switch 4
                     -----------------------------------------
                           16 Kb            ON           ON
                           32 KB           OFF           ON
                           48 KB            ON          OFF
                           64 KB           OFF          OFF
                       96 - 256 KB         OFF          OFF
                                                       
       5,6  -  Indicates Initial Video Mode for the connected
               displays. Settings are:

                      Display Type        Switch 5   Switch 6
                   ------------------------------------------
                   Monochrome               OFF        OFF
                    (single display)
                   Monochrome + another     OFF        OFF
                    display
                   Color (40 X 25)          OFF         ON
                   Color (80 X 25)           ON        OFF

       7,8  -  Show the number of floppy drives attached, assuming
               Switch 1 is set properly. Indications are:

                   # of floppy drives      Switch 7   Switch 8
                  --------------------------------------------
                         0                   ON          ON
                         1                   ON          ON
                         2                  OFF          ON

    I;m really not sanguine about going into the memory permutations
and all the switch settings for SW2. I note that regardless of memory
installed, Switchs 6, 7 & 8 of SW2 are ALWAYS in the "ON" position.
The other 5 switches start as all "ON" for total memory less than or
equal to 64 KB and go from there, changing as memory is added. E-Mail
me of you want info on a particular configuration.

     Hope this helps.

Unky Dave
unkydave@shumv1.ncsu.edu