Re: 6510 replacement

On 2012-09-16, at 21:48, Spiro Trikaliotis wrote:

>> how to replace 6510 with 6502 combined with a port chip or something
> 
> Note, this has already been done in the 64'er (I cannot remember the
> exact issue, though).

On 2012-09-16, at 22:01, Mike Naberezny wrote:
> 
> It's in the file c64-2MHz.zip here:
> 
> http://www.zimmers.net/anonftp/pub/cbm/documents/projects/accelerators/

Another perfect example why I like this list so much ;-)

I got the file. Yes, it's been done for a different reason there but one thing made me wonder. Why (as long as I don't want to double the clock) things can be less complex than the published solution, I still need cassette port working. The description says though:

"The 6510 features a 6bit wide I/O port that is used for communicating
    with the tape drive and the MMU. The tape drive support is skipped here
    due to excessive hardware need."

Putting aside that it's an 8-bit port with two bits unused, huh... wondering if by "excessive hardware need" they mean doubling the circuitry for additional three bits or something even more "excessive"?

> Also, have a look at the VIC20 schematics, it has the same circuitry.

But it doesn't have all the features of a 64/6510, does it? I mean AEC, the $00/$01 port, tape is connected to VIA..

You mean which circuitry is the same? What can I learn from it that could be used in a 64 to implement the missing elements?

-- 
SD!
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