View source for KernelDebugRef - Debugging VM Start Sessions

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<p>Before you begin debugging in a VM Start session, you must establish interrupt vectors 1 and 3. Issue the command DD %%0 to see what the vectors should be, and then issue the following commands to set them to their correct values:</p>
           E &0:4 12 67 00 1d
           E &0:c 57 67 00 1d
<p>To debug a trap 6 or an incorrect-output problem, set a breakpoint at the <h2>VMINT21</h2> entry point.</p>
<p>You can find the segment of FSFILTER by looking at the <h2>INT 20h</h2> or <h2>INT 21h</h2> vectors (0:80 and 0:84, respectively). The offset of <h2>VMINT21</h2> is hex 330. Trace through all of the <h2>INT 21</h2> calls until the error is observed. Run the test again to the last successful <h2>INT 21</h2>, then begin stepping through the code until the error is found.</p>
<p>A method of eliminating FSFILTER as the component with the problem is to set up a test case that is executed from the diskette. This way, you can execute a VM Start session without installing FSFILTER. If the problem still occurs, then FSFILTER is not the cause of the problem.</p>