Tech Note 009 - 64-bit Oberon0

Adapting the Oberon07 compiler and Oberon OS to 64-bits

Much has been done before: https://www.modulaware.com/mdlt68.htm https://github.com/vishaps/voc
Same compiler source should compile on 64 and 32 bit systems
64 and 32 bit compilers should compile 64 and 32 bit code equivalently
LONGINT should accept a system pointer, therefore follows system register size

Extending RISC5 to 64-bits (erisc5)

registers R0 through R15, PC, H, SPC extended from 32-bit to 64-bit
32-bit opcodes unchanged
64-bit word loads and stores alingned to 32-bit boundaries
64-bit memory-mapped device registers take double the space

General OS considerations for 64-bit

start of general use system RAM may not be 0 (0x00200000 on Pinebook Pro, for example)
Method Table entries for 64-bit Oberon take 8 bytes instead of 4 bytes for 32-bit Oberon
Method Table start at start of system RAM + 64 bytes for 64-bit Oberon
In 32-bit RISC5 Oberon there is space for 31 MT entries (through byte address 255.)
64-bit Oberon may reserve space for 1008 entries (up to Start of System RAM + 8192 bytes.)
32-bit Oberon may also reserve space for 1008 entries (up to Start + 4096 bytes.)
First 32 or 64 bytes are implementation dependent and reserved (e.g. for reset vector, etc.)
Kernel.Mod for each platform is platform dependent and will define interrupt vectors, mmu tables, etc. as appropriate.
On hardware providing u-boot, Kernel.Mod may retrieve useful configuration information from a Device Tree Blob.
On hardware providing UEFI, Kernel.Mod may retrieve useful information from the firmware.
Module records are 32 bytes + 12 words = 80 bytes for 32-bit systems or 128 bytes for 64-bit systems.
Structures in Files.Mod and FileDir.Mod require adjustment for 64-bit integers, technote 004 describes a 64-bit Oberon filesystem.