Andrew Gale wrote: > but what if it is playing silly buggers with the SP and > some important section of memory gets overwritten? Is this > just very unusual and tough luck when it happens?
For the original Spectrum versions it was just tough luck. I frequently remember the pushed values being visible on the display when used for fast tranfer routines, and even corrupting game sprites. I was always fearful of snapshotting games to save my position because of what could be scribbled on! I also wrote some anti-multiface code in a password program I wrote yonks ago, which avoided using the stack completely so I could leave SP pointing to a ROM location. When the multi-face was activated the PC value shown was constant junk, so it wasn't possible to tell where the running code was, and so the program couldn't be resumed. > I'm trying to decide whether or not to guard against this by > preventing the PC from being written to the SAM's RAM and > catching the values in some special latches instead... Would be very nice if it could be done! Si
