Re: Gemini 80-Bus System
Here is a useful "trick" for xbeaver.
xbeaver supports mulltiple named io buses. The default bus the processor uses is called "io". However peripherals can be placed on a different bus. The internal bus extender can be used to map these io ports through to the "io" bus with various mappings. The internal bus extender also has the ability to trace bus cycles.
Looking at the gem925.cfg below - the "trace" bus is used for io and the bus bridge is used to map these to the io bridge. This gives the ability to selectively trace bus cycles.
Best shown by example....
#verbose
cpuclock 4
board 0x00 intbus 0 0xfb xrw trace
board 0xfb intbus 0xfb 2 xrwt trace
board 0xfd intbus 0xfd 3 xrw trace
bus trace
board 0xfe gm813_mmu
board 0xb0 gm832 Gemini green
board 0xb8 serial_8250 trace tty tty /dev/ttyS0
board 0xe0 gm849_scsi ~/beaver/disks/gem925.dsk
board 0xfb gm833
board 0xe0 gm849_floppy -geometry D35.2.10.0.512 ~/beaver/gm512/GM512_ORIGINAL.DMP
bus io
binload cb00 ./beaver/network/cpm64w.bin
byte 0 c3 00 eb
By running this it is clear that the bios is looping writing to all tracks with sector=0. I would guess this is sizing the ramdisk.
Unfortunately the emulator works by allocating more memory to the ramdisk as required (upto MByte). I suspect the gemini software is just looping trying to find the end of the ramdisk and failing.
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