Electronics > Projects, Designs, and Technical Stuff

Found a weird old computer dumpster diving. (z80?)

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tsvisimcha:
Under the speaker

tsvisimcha:
Another angle

tsvisimcha:
I have a bus pirate somewhere so I can try to dump the eeprom if someone wants to take a look at it.

rstofer:

--- Quote from: tsvisimcha on March 28, 2020, 05:54:54 pm ---I have a bus pirate somewhere so I can try to dump the eeprom if someone wants to take a look at it.

--- End quote ---

Disassembly from a ROM dump is a fool's exercise.  All the author needs to do is put in some bogus 0x21 (LXI  H) bytes to throw off disassembly.  The next two bytes would be an operand for the LXI H but are actually the start of some other instruction because the LXI H is never executed.  The BDOS component of CP/M has this feature.  Or at least that's what I came up with when I tried to disassemble it.  The first byte of any other multi-byte instruction will do the same thing.

Just scatter so DB 0x21 instructions in the code.

rstofer:
It might be better to remove the speaker completely.  The Z80 and the NVRAM are pretty sweet.  I don't care for desoldering but I might make an exception.  I have several Z80 systems including a complete CP/M system running on a 50 MHz eZ80.  The system just screams at that speed!

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