Leslie Ayling wrote: > I was curious if anyone has any information on what use > ProDOS 2.0.3 makes of the Alternate 64k bank on an > extended 80 column card. Yep. The major use is the /RAM volume and associated control information. The Enhanced IIe firmware (and probably ProDOS as well) also has conventions for dealing with interrupts that occur while the alternate stack and zero page are active, which involves the use of saving and restoring main and auxiliary stack pointers in locations $0100 and $0101 in auxiliary memory. According to the ProDOS-8 Technical Reference manual, the following memory areas are reserved in auxiliary memory: $0080 to $00FF (used by ProDOS) $0200 to $03FF (used by ProDOS) $0400 to $07FF (text page 1A) $BF00 to $BFFF (reserved) $D100 to $DFFF in language card bank 2 (reserved) $E000 to $FFFF in the language card (reserved) There is further information in ProDOS-8 technical note #26 (Polite Use of Auxiliary Memory). If /RAM is enabled, the application can disable it and use all auxiliary memory above $0800. If /RAM is not enabled, the application must obey the above restrictions for memory above $0800. The area from $D100 to $DFFF is reserved for third party RAM disk drivers. The $E000 to $FFFF block is used by one version of Apple II SANE (Standard Apple Numerics Environment). According to this technical note, auxiliary memory below $0800 is always reserved and should never ben used by an application. The main problem is likely to be conflicts with third party RAM disk drivers. It is not clear what the rules are if you are writing such a driver, since Apple never released a promised technical note which would have clarified this. There is some extra code for the /RAM driver in the $0200 area. The supported facility for disconnecting and reconnecting /RAM requires that this area be left alone. I expect the reserved area of auxiliary zero page is also used by the /RAM driver. -- David Empson dempson@actrix.gen.nz Snail mail: P O Box 27-103, Wellington, New Zealand