What value should DMAMask be ?
Read the instructions that came with your computer or disk controller. Can it access all memory on your machine ?
If this doesn't help look at your memory map with ShowConfig. Use the maximum memory address as a starting point and adapt it as follows :-
Please look at the above paragraph. If you use MapROM you should check your value as the address quoted by ShowConfig contains a 7 which should be changed.
The following table gives some examples :-
Address | DMAMask ------------+------------ 0x001FFFFF | 0x001FFFFC 0x005FFFFF | 0x007FFFFC 0x07FCFFFF | 0x07FFFFFC 0x07FFFFFF | 0x07FFFFFC
If you add memory to you machine you should review you DMAMask settings BEFORE you install the memory ! Another, poorer, option is to set the DMAMask to 0xFFFFFFFC from the word go. This is option is NOT available if your disk controller needs a specific type of memory. See above.