tom@vrdxhq.UUCP (Tom Welsh) (09/02/86)
For those of you who have old Davong cards (i've seen some requests),
in PC 1's, here's the "IBM PC Memory Expansion Cars Documentation"
I got from Davong.
(Remember that old PC 1's have two switches SW1 and SW2)
" . . . SW1 must always be set for 64k on the
system board. The setting for SW2 will depend on the amount
of contiguous memory the system will have after installation
of the new memory expansion card.
To determine the switch settings for the IBM SW2 switch block, you must
add the total amount of memory currently in the system to the
amount to be added by the new memory expansion card.
If a 64k byte expansion card is being added to the system with only
64k, then the total memory for the system would be 128k and IBM SW2 would be
set to a total memory size of 128k (1-on, 2-off, 3-on, 4-on).
IBM System SW 1
+----------------------------+
| 1 2 3 4 5 6 7 8 |
| on |
|off * * |
+----------------------------+
IBM System switch SW2 -- switches 1 thru 4 must be set to indicate
the TOTAL contiguous memory on the system including the 64k bytes on the main
board and any expansion memory boards. A listing of the common switch
settings is given below.
Total Memory IBM SW2 Switches
128k bytes +----------------------------+
| 1 2 3 4 5 6 7 8 |
| on * * * |
|off * |
+----------------------------+
192k bytes +----------------------------+
| 1 2 3 4 5 6 7 8 |
| on * * * |
|off * |
+----------------------------+
256k bytes +----------------------------+
| 1 2 3 4 5 6 7 8 |
| on * * |
|off * * |
+----------------------------+
320k bytes +----------------------------+
| 1 2 3 4 5 6 7 8 |
| on * * * |
|off * |
+----------------------------+
384k bytes +----------------------------+
| 1 2 3 4 5 6 7 8 |
| on * * |
|off * * |
+----------------------------+
448k bytes +----------------------------+
| 1 2 3 4 5 6 7 8 |
| on * * |
|off * * |
+----------------------------+
512k bytes +----------------------------+
| 1 2 3 4 5 6 7 8 |
| on * |
|off * * * |
+----------------------------+
DAVONG Memory Expansion Card Switch Settings
Default Switch settings
The default switch setting for each memory size of the DAVONG Memory
expansion cards is given below. Check that the switches on your card match
those for that memory size. If a setting other than the default is
to be used, the non-standard switch settings may be used. These are documented
following the default settings.
-- 64k bytes -- the switches are set to indicate a start address of
64k and a stop address of 128k
+----------------------------+
| 1 2 3 4 5 6 7 8 |
| on * * * * * * |
|off * * |
+----------------------------+
(stop address of 128k) (start address of 64k)
-- 128k bytes -- the switches are set to indicate a start address of
64k and a stop address of 192k
+----------------------------+
| 1 2 3 4 5 6 7 8 |
| on * * * * * |
|off * * * |
+----------------------------+
(stop address of 192k) (start address of 64k)
-- 192k bytes -- the switches are set to indicate a start address of
64k and a stop address of 256k
+----------------------------+
| 1 2 3 4 5 6 7 8 |
| on * * * * * * |
|off * * |
+----------------------------+
(stop address of 256k) (start address of 64k)
-- 256k bytes -- the switches are set to indicate a start address of
64k and a stop address of 320k
+----------------------------+
| 1 2 3 4 5 6 7 8 |
| on * * * * * |
|off * * * |
+----------------------------+
(stop address of 320k) (start address of 64k)
Non-standard switch settings
For stop and start addresses other than the default, the swithces must be
set to match the user requirements. The switch functions and the table of
the addresses versus switch settings should be used to determine the
correct settings.
Switches 1 thru 4 set the stop address
Switches 5 thru 8 set the start address
If there are additional memory boards in the system, then the start address
and stop address would have to be modified to place this board address above
the existing memory.
Address
Switch Bit
------ -------
1 stop 19
2 stop 18
3 stop 17
4 stop 16
5 start 19
6 start 18
7 start 17
8 start 16
The 'on' position corresponds to a logical '0' for that address
line. During system operation, the memory card is selected by a memory
read or write when the high four I/O channel address lines are within
the range set by the start and stop address switches.
DSI memory cards come in sizes starting at 64k bytes and reaching
256k bytes in 64k byte increments. The banks on the printed
circuit card are filled sequentially from bank 1 through bank 3.
On the user expandable cards, the banks must also be filled in sequentially
from bank 1 through bank 3. All nine sockets in each bank being used MUST
have a memory chip in it to operate correctly. As the memory chips are added,
the Stop address switches on the board must be modified to correspond to
the new ending memory address and the IBM switch settings must be changed
to reflect the new total memory size."
Disclaimer:
I make no claims for the above Davong memory documentation. I installed
a card in my Compaq deskpro. The Deskpro came with 256 on the mother board.
I made no changes to the mother board switches. I set the Davong board,
per above, to start at 256k and end at 512k. It works fine!