Re: Hardware emulation of 6509 using 6502?

From: Jim Brain <brain_at_jbrain.com>
Date: Thu, 19 Jul 2018 21:47:42 -0500
Message-ID: <7b57caab-f33a-eaca-7d35-8674faa9a501@jbrain.com>
On 7/19/2018 3:17 PM, Mia Magnusson wrote:
>
> Well, phi1 and phi2 being swapped in the data sheet were discovered
> this year, so ;)
Touche'
> The question is which devices do depend on this?
Ruud will have to answer.
>
> There is already an 18MHz clock on the B motherboards, so except for
> the P, it's easy to obtain a synchronized clock with higher frequency.
> In fact, using an adapter on top of the timing shift register gives 9
> states throughout the 2MHz cycle of the CPU clock, and by using both
> flanks of the 18MHz clock you can get 18 steps within each 2MHz period
> cycle.
>
> Of course it would be more cumbersome for a user to have to solder a
> wire or add some clip-on-thing, but using this in a hypothetical future
> B replacement/replica motherboard would be trivial.
Yes, but the likelihood that someone will use it goes up markedly the 
fewer things they have to jumper or solder.

Jim


-- 
Jim Brain
brain@jbrain.com
www.jbrain.com
Received on 2018-07-20 05:00:05

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