Gigatron Hackers

Also, the file format doesn't allow a write to page 0 other than the first segment, but a loader can do whatever it wants. What if the loader writes the start address minus 2 and the start address minus nothing to the vPC and vLR in page 0, and not send the start command. Wouldn't the return from th...

After loading the start address into vLR, can't you just RET?

Doesn't the loader use SYS_LoaderProcessInput_48 which does the subtraction of 2 from the start address and stores it in vPC and vLR? That routine is in ROM, and can't be patched.

I generated a trace of vcpu instructions from Gigatris.gt1 using the javascript emulator and saw this (the value after the ... is the virtual link register): 0200 cd39 DEF 39 ... 02fe 023b 2b3a STW 3a ... 02fe 023d cd56 DEF 56 ... 02fe 0258 2b3e STW 3e ... 02fe 025a cda0 DEF a0 ... 02fe 02a2 2b4a ST...