neals@midas.UUCP (Neal Sedell) (01/07/87)
Well, now that I've had another late night/morning to play with things, it would seem that OS9 does load itself into the uppermost 64K... The screen driver from another sorce was CHANGING both the first and second MMU entries..... While I was as it I discovered that using the first MMU entry is not as good an idea as I had thought. As a matter of fact, it's not a good idea at ALL!!! After several hours of messing with co80, reassembly, OS9GENing and crashing on bootup, I finally gave up and tried using the second MMU entry. When that worked I called it quits. This morning it finally dawned on me that the stack pointer might be down there. A quick check with DEBUG showed that the stack starts around $A00 or so and was being swapped out in mid subroutine. How embarassing. Oh well. Maybe the last MMU entry doesn't look so bad after all, except that if your driver lives there it's bye bye. I'm sure both CO80 and the ramdisk load well below $E000 if near the start of the boot file. When I expanded co80 to 25 lines I changed the 80x24 table entries for lines/row to 9 and lines displayed to 225. I think that changed the mono+3 to mono+4 and the $15 to $75 - I'll check and re-post if wrong. Other mods I anticipate are changing NEWDISK to slow cpu speed down on entry then speeding up on exit, since it or the hardware doesn't seem capable of reliable high speed operation. And taking out the speed switching code from co80. Sure is nice to have the sources! Neal Sedell