Re: [Atari800-users] Is ROM truly ROM in atari800?

[<zy...@po...>]

Hello Dan,




Yes, it is true that some cartridges do STA into the cartridge address 
space, verifying if the address space dedicated for cartridges is read-only.

This could have been used as a simple anti-piracy measure. The memory 
management unit of the 8-bit Atari computers ensures that, when a cartridge 
is present, data go only to the cartridge and not to the computer's RAM 
chips. And since the cartridges hold ROM, the writes are effectively 
ignored.




When it comes to .ATRs, these are floppy disk images, so the emulator treats
them as a floppy disks inserted in a disk drive. Of course, real floppy 
disks had write protection capability - either piece of adhesive tape 
covering the write enable notch, or a sliding write protection tab. The .ATR
files have a bit in them indicating if the write protection is on or off. 
The floppy drive emulated by atari800 honors the write protection bit. Also 
allows you to open the .ATR file as read only, regardless the bit.




Michael


"


Hi.




I think some atari800 cartridges like to STA into the code in their ROM 
region with an invalid instruction, to deter copying.




Does atari800 treat .atr's as ROM?




Thanks for the cool emulator :)






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