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- Quarterdeck Technical Note
-
- Patching QEMM 50/60 version 4.03 to support IBM 2-8Meg Memory
- Expansion Option Boards.
-
-
- Background: QEMM 50/60 version 4.03 was released prior to the
- release of the IBM 2-8Meg Memory boards and run as-is, will not
- support these boards. However following a simple debug patch,
- 4.03 will support the boards and the patch does not effect any of
- the support of the driver for other boards.
-
- THE PATCH
-
- First, make sure you have a PATH set to your DEBUG.COM file which
- is part of your DOS files and is usually located in your DOS
- directory. Switch to the directory containing QEMM.SYS (usually
- the root directory) and type in the following to start DEBUG and
- load the QEMM.SYS driver.
-
- C:\>debug qemm.sys
-
- After loading, DEBUG returns a minus sign (-) as a prompt.
-
- First we want to identify the spot where the patch will be made
- and verify that we are patching the correct driver. To do this
- type in the following:
-
- -d 3374 L 8 <--- Hit Enter
-
- Debug will display something like the following. The part that
- is shown as xxxx will be some hex number that we are not
- concerned with.
-
- xxxx:3370 FF FF FE FE-11 6B EE 6B
-
- If the numbers shown above after the "3370" do not match what
- your copy of QEMM.SYS shows you, do not proceed with the patch.
- You are probably working with a version of QEMM prior to 4.03,
- which cannot be patched, or a later release which does not
- require the patch. Assuming the numbers match, type in the
- following:
-
- -e 3376 <--- Hit Enter
- You will get a display similar to the one below except the
- display will be paused after the "FE." and will be waiting for
- input. Type in the "F7" and hit the space bar. Debug will then
- tab over and display another "FE" and again pause for input. Type in
- "F7" and hit the spacebar again. The cursor will drop to the
- next line, display another set of HEX numbers ending in "11" and
- again be waiting for input. Complete the patch by typing in the
- remaining numbers in the patch with a spacebar in between as
- follows:
-
- 01 {spacebar} 6D {spacebar} 47 {spacebar} 6E <--- Hit Enter
-
- Verify that the patch has been made correctly by repeating the
- inspection process above by typeing:
-
- -d 3374 L 8 <--- Hit Enter
-
- If the patch was made correctly, the output should look like
- this:
-
- XXXX:3370 FF FF F7 F7-01 6D 47 6E
-
- If it does not, you did the patch incorrectly and should type
- "Q", hit the Enter key, which will put you at the DOS prompt and
- start again.
-
- Assuming the patch looks correct, type "W" to the "-" prompt and
- hit Enter to write out the change .
-
- Debug will indicate that it is writing out the change.
-
- Writing xxx bytes
-
- Type "q" to quit out of Debug.
-
- -q
-
- You will get the DOS prompt and you are done. Now boot your
- machine with the patched QEMM.SYS and it should recognize your
- 2-8 meg board.
-
- * * * E N D O F F I L E * * *