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03 March 2012, 13:15
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#1 |
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Registered User
Join Date: May 2006
Location: France
Age: 48
Posts: 211
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ExecBase
Hello, I am new to amiga operating system and I am not sure to understand well how the ExecBase structure works.
The addresse of this structure lies at address 04. But 04 is the address where normally goes the reset routine. So after a reset the PC continue execution at the address that is at address 04. But at ExecBase, the first field id LibNode and that is not an executable instruction, so I'm not sure to understand it correctly |
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03 March 2012, 15:01
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#2 |
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Registered User
Join Date: Jan 2002
Location: Germany
Posts: 7,002
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After power-on the ROM is shadowed at the low memory area so that the processor finds executable code at address 4. The code then jumps to the real ROM address at $fc0000 and the shadow is removed to that the RAM becomes visible. After that ExecBase is initiallised and its address is written to $4. ExecBase is a normal library base with the data section at positive offsets and the jump table at negative offsets.
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24 March 2012, 00:01
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#3 |
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Registered User
Join Date: May 2006
Location: France
Age: 48
Posts: 211
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OK thanks thomas
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