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More details on regenerating ROM images

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Jeff Parsons 2015-04-06 16:56:27 -07:00 • committed by jeffpar
commit 960c85acbc
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10
devices/pc/bios/compaq/deskpro386/README.md
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@ -65,15 +65,19 @@ there are exceptions to that general rule.
Producing BIOS Source Code
---
In the current directory, I ran NDISASM (the disassembler included with NASM):
In the current directory, an original ROM can be regenerated from the JSON-encoded file:
ndisasm -o0x8000 -se105h -se05ah -se6ffh -sf025h -sf8aah private/1988-01-28.rom > 1988-01-28.nasm
node ../../../../../modules/filedump/bin/filedump --file=1988-01-28.json --output=1988-01-28.rom --format=rom
The ROM can then be fed into NDISASM, the disassembler included with NASM:
ndisasm -o0x8000 -se105h -se05ah -se6ffh -sf025h -sf8aah 1988-01-28.rom > 1988-01-28.nasm
The `-o0x8000` argument is required to "org" the file at the proper starting address, but the `-s` arguments
are optional; they simply establish a few sync points within the ROM image that save a little cleanup effort, by
preventing disassembly in the middle of instructions.
Then I ran the PCjs [TextOut](/modules/textout/lib/) command, with the *--nasm* option, to prepare the code for reassembly:
Next, the PCjs [TextOut](/modules/textout/lib/) command, with the *--nasm* option, prepares the code for reassembly:
node ../../../../../modules/textout/bin/textout --file=1988-01-28.nasm --nasm > temp.nasm
mv temp.nasm 1988-01-28.nasm