Re: has anybody tried to replace a vic or vic II chip with a board containing a propeller ?

From: Segher Boessenkool <>
Date: Sun, 26 Feb 2012 17:53:56 +0100
Message-Id: <>
>> The biggest problem in faithfully emulating a VIC-II on a CPU is
>> the pixel logic: 8M times per second you need to combine the eight
>> sprites and the video matrix using the multi-colour and priority
>> regs, select which colour to display, and update the sprite
>> collision registers. Everything else requires much less bandwidth:
>> if you have no sprites at all on the video chip you're emulating,
>> it's much easier.
> Hm, I would have expected another big problem to be the emulation  
> of the tricks of the VIC-II that are a sideeffect of the logic used  
> in it. I mean opening the border and other 'undcoumented' features.

Not really no, all that happens when you write to registers, i.e.
you have at most one of those per 1MHz clock, so not very tricky
to get fast enough on a CPU.  Of course you have to know exactly
how the VIC-II works internally, but we have die pics...


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Received on 2012-02-26 17:00:35

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