Martin Eberhard <
mfebe...@gmail.com> writes:
>If anyone's interested, I just disassembled the BIN loader that's in RIM fo=
>rmat at the beginning of the EDUSYSTEM 20 paper tape.=20
>
>This loader is kind of interesting. When the RIM loader loads this BIN load=
>er, the RIM loader gets modified to jump to this BIN loader when the RIM lo=
>ad is done. Then this BIN loader repairs the RIM loader, undoing this modif=
>ication.=20
>
>It then pulls the KSF and KRB instructions from the RIM loader and pastes t=
>hem into its own code, so that the BIN loader loads from the same device as=
> the RIM loader did - whether its the console TTY, a high-speed paper tape =
>reader, or even another serial port at a different address. This is kind of=
> cool - in my case, I've modified my RIM loader to load from a 9600 baud se=
>rial port, with KRB at 6306 (distinct from the console TTY at 6036). Even w=
>ith this modified RIM loader, EDUSYSTEM 20 loads and runs perfectly on my P=
>DP-8e.
>
>There is a strange bit of code at the beginning of this BIN loader that loo=
>ks like it is intended to copy itself into another memory field and then ju=
>mp there. But as found, it copies from field 0 to field 0, so it doesn't ac=
>tually do anything useful. I suspect this BIN loader was used for other DEC=
> applications, where the the field in which it is loaded by the RIM loader =
>is different than where it wants to run.
>
>Anyway, if you are interested, you can find my disassembly here. I've tried=
> to be pretty verbose, explaining how it works in the comments:
>
>
https://deramp.com/downloads/mfe_archive/011-Digital%20Equipment%20Corporat=
>ion/30%20DEC%20Software/Edusystem/Edusystem%2020/
>
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