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Old 07 June 2013, 22:37   #12
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Join Date: Jan 2012
Location: USA
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Originally Posted by phx View Post
Ok. The only question here is whether the number of available memory cycles until DDFSTART are sufficient to load the pointers for all five bitplanes, write the COPJMP and COLOR.
If you're very desperate, you can use the CPU to change the bitplane pointers. The Amiga CPU interrupt mechanism is very clever and allows the CPU to be well-synced to the display if necessary. This means you can pre-load registers with data, STOP the CPU, trigger an interrupt with the copper, and then blast the hardware registers using a MOVEM.L instruction. There is quite a delay between the interrupt and moment the CPU begins to write to the registers, but it is predictable for a 68000 with the interrupt handler and supervisor stack in chipram. Other processors introduce complications, though.
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