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74 lines
3.3 KiB
Markdown
74 lines
3.3 KiB
Markdown
# Assembling Collapse OS from within it
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This is where we tie lose ends, complete the circle, loop the loop: we assemble
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a new Collapse OS *entirely* from within Collapse OS and write it to EEPROM,
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either for another RC2014 or for an OS upgrade.
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## Gathering parts
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* stage3 from `sdcard` recipe. If you want to write to EEPROM as the final step,
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you'll need a hybrid stage3 that also includes stuff from the `eeprom` recipe.
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## Building the binary
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Build Collapse OS' from within Collapse OS is very similar to how we do
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it from the makefile. If you take the time to look at the base recipe
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`Makefile`, you'll see `cat xcomp.fs | $(STAGE)`. That's the thing. Open
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`xcomp.fs` in a text editor and take a look at it. You'll see that it loads
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B599, which contains the meat, and then spits stuff to port 2, which is a
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special signal for the `stage` binary.
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To assemble from RC2014, all you need to do is load B599. This will
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yield a binary in memory. To know the start/end offset of the binary, you'll
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type the same two commands and in `xcomp.fs`, but replace the `/MOD 2 PC! 2 PC!`
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words with `.X`. Then, write that binary between those offsets on your target
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media. That binary should be the exact same as what you get in `os.bin`
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when you run `make`.
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Go ahead, run that. However, one thing you should know is that because the SD
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card driver is a bit slow, some of these commands take a long time. Multiple
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minutes. Be patient.
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Is that it? Yes. But for your own enlightenment, open B618 and look at it, I'll
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give you an overview of its contents. I'm not going to explain in detail what
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each command do, however. You are encouraged to read the in-system
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documentation for more information.
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The first part is configuration of your new system. When RAM starts, where RSP
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and PSP start, what ports to use for what device, etc. These configuration
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declarations are expected in the boot code and driver code.
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Then, we load the Z80 assembler and the cross compiler (xcomp for short), which
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we'll of course need for the task ahead.
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Then come xcomp overrides, which are needed for xcomp to be effective.
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At this point, we're about to begin spitting binary content, this will be our
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starting offset. `ORG` will soon be set to your current `H@`.
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Then, we assemble the boot binary, drivers' native words, then inner core,
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close the binary with a hook word. We're finished with cross-compiling.
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We're at the offset that will be `CURRENT` on boot, so we update `LATEST`.
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Then, we spit the init source code that will be interpreted on boot.
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And... that's it!
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### What to do on SDerr?
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If you get `SDerr` in the middle of a LOAD operation, something went wrong with
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the SD card. The bad news is that it left your xcomp operation in an
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inconsistent state. The easiest thing to do it to restart the operation from
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scratch. Those error are not frequent unless hardware is faulty.
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### Verifying
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You can use `/tools/memdump` to dump the memory between your begin/end offsets
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so that you can compare against your reference stage 1. Before you do, you have
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to take yourself out of xcomp mode. First, run `XCOFF` to go back to your
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regular dict. Then, run `FORGET CODE` to undo the xcomp overrides you've added
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before. That will rewind `HERE`. You don't want that. Put `HERE` back to after
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your ending offset so that you don't overwrite your binary.
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Then, you can run `/tools/memdump`.
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