OS_Byte CMOS Settings

OS SWI Calls

» OS_Byte

» OS_Byte CMOS Settings

Notes

RISC OS provides 240 bytes of data to be stored in non-volatile memory. Much of the storage is reserved for future use, however, it does provide a method of storing key system configurations such as for expansion cards and so forth.

CMOS usage is subject to change depending on different versions of RISC OS, and applications should not assume the location of any particular byte address. Software should try to use higher-level APIs to read or write system settings, rather than altering CMOS directly.

Controlling sources: Hdr:CMOS managed by the allocations manager

¹ Locations which are reserved for the user can be freely used by user software. However because use of this region of CMOS is not regulated, in order to avoid clashes software which uses these locations should not be publicly distributed.

² Locations which are reserved for applications can be used by third-party software, providing an allocation has been made. However with a hard disc and !Boot sequence being standard features on modern machines, it’s recommended that software stores its configuration in the Choices folder instead.

³ Expansion cards can determine the size and number of CMOS bytes available for their use by using the Podule_ReadInfo? and PCI_ReadInfo SWIs. Note that configuration data is not automatically wiped when the user moves expansion cards from one slot to another – and so a newly installed card may be reading old configuration data left behind by a previous card. It is the card driver’s responsibility to cope with this, e.g. by correctly detecting and ignoring invalid configuration settings.

See also

• OS_Byte