Alrighty, lets pretend we are showing a res of 512x384... and at 1bit per pixel, this leaves us with a video buffer size of 24kilobytes...
lets divide that buffer by 3 (since you have three sections showing on your screen) , this will give us an 8kilobyte chunk...
assuming we were running with 128kilobytes of ram... our primary video buffer would start at address 0x1A700
0x1A700 - 0x1C6FF 1st third of video buffer
0x1C700 - 0x1E6FF 2nd third of video buffer
0x1E700 - 0x20700 3rd third of video buffer + primary audio buffer
since the 2nd third and the 3rd thirds are repeating and you have distorted sound... it looks like either VA13 or AX13 is stuck low causing the 1st third of the screen to show part of the stack.... the second third of the screen to show the correct area, and the 3rd area of the screen to repeat the 2nd third's buffer... and to generate audio from the end of the 2nd thirds buffer data.
Check the following:
VA13 stuck low on:
pin 11 of U1G, 74393
BMU0
AX13 stuck low on:
pin 4 of U3G, 74253
BMU0, pin 14
pin 10 of U2F 74257
lets divide that buffer by 3 (since you have three sections showing on your screen) , this will give us an 8kilobyte chunk...
assuming we were running with 128kilobytes of ram... our primary video buffer would start at address 0x1A700
0x1A700 - 0x1C6FF 1st third of video buffer
0x1C700 - 0x1E6FF 2nd third of video buffer
0x1E700 - 0x20700 3rd third of video buffer + primary audio buffer
since the 2nd third and the 3rd thirds are repeating and you have distorted sound... it looks like either VA13 or AX13 is stuck low causing the 1st third of the screen to show part of the stack.... the second third of the screen to show the correct area, and the 3rd area of the screen to repeat the 2nd third's buffer... and to generate audio from the end of the 2nd thirds buffer data.
Check the following:
VA13 stuck low on:
pin 11 of U1G, 74393
BMU0
AX13 stuck low on:
pin 4 of U3G, 74253
BMU0, pin 14
pin 10 of U2F 74257