Revision as of 07:43, 6 April 2025 view source Retroand (talk \| contribs) Bureaucrats, Interface administrators, Administrators 666 edits →‎Diagnostics ← Older edit		Revision as of 08:04, 10 April 2025 view source Retroand (talk \| contribs) Bureaucrats, Interface administrators, Administrators 666 edits Corrected ROM capacity description Newer edit →
Line 89: \|} [[File:ROS Memories.jpg\|thumb\|left\|alt=Some of the sixteen ROS memories\|Some of the sixteen ROS memories]] The ROM Operating System or simply ROS is the firmware of the System/23. It consists in a set of fourteen to sixteen ROMs of 8KB each, for a total of 112KB/128KB, although the service manual states 112KB which means they did not ~~count~~update the ~~non-paged~~capacity after adding ROMs 10h ~~ROM~~and ~~memory~~11h<ref>SY34-0171-0 IBM 5322 Computer Service Manual, page 74</ref>. Each ROS ROM has a unique diagnostics identification code, which is determined by the outputs of two 74LS138 3:8 decoders. ROMs 02h and 09h are fixed in the memory map, where the rest are paged in the memory range 4000h-7FFFh. ROMs 0Eh and 0Fh are not present but the logic to select them is implemented even if there is no place to place them in the board; still, with an appropriate ROM adapter their space could be enabled to inject code into the system. ROMs paged 0-7 are present in the board while ROMs paged 8-15 are expected to be provided by expansion cards on their corresponding slots. Therefore, the maximum theoretical ROM capacity for the Datamaster consists of 272KB if the 0Eh-0Fh gap and pages 8-15 are used.

IBM System/23 Datamaster: Difference between revisions