Re: Hardware emulation of 6509 using 6502?

From: smf <smf_at_null.net>
Date: Wed, 7 Mar 2018 16:31:41 +0000
Message-ID: <96cdabf8-153e-aaae-77a7-0b7711363af9@null.net>
On 07/03/2018 16:23, Mia Magnusson wrote:

> Is it just as simple as screen + color ram is read in the "CPU"
> phase of the clock cycle ("bad line" in C64 lingo), and char data /
> bitmap data and sprite data is read during the "VIC" phase of the clock
> cycle?
I believe so. VIC is quite predictable.
> I really don't understand why there is a need to split theese cycles
> though.

The designer thought it was a neat solution at the time?

They needed to be able to differentiate character generator rom and 
screen fetches. The c64 does it with magic addresses, which is quite 
limiting itself.



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Received on 2018-03-07 18:05:24

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