Re: Ribbon Cable

On 12/18/2013 01:38 AM, Jim Brain wrote:
> On 12/17/2013 4:24 PM, Gerrit Heitsch wrote:
>> On 12/17/2013 10:59 PM, Bil Herd wrote:
>>> Several of the times when  I tried to "clean up" this kind of thing for
>>> the C128 I would come across a compatibility issue; we found that third
>>> parties had used the glitches on IO lines to latch R/W and that some
>>> carts
>>> like the Magic Voice cart would drive the bus at unexpected times
>>> including the high address lines (They would toggle /GAME and /EXROM
>>> dynamically when the system had been designed for them to be solder
>>> jumpers).  Eventually I stopped trying to "improve" it and try to
>>> learn to
>>> "live with" it.
>>
>> There are other carts that are guilty of that... The feature of the
>> Easy Flash 3 that lets you use a KERNAL on the Expansionport without
>> having to remove the internal one or any internal soldering needs
>> dirty tricks like this.
>>
>> See here:
>>
>>  skoe.de/kernal/kernal-cartridge.pdf
>>
>> Some people like it, I don't.
> Everyone's entitled to their opinion, but I think the *hack" in EF3 is
> what groups like cbm "hack"-ers would appreciate.  One could say the
> same thing about the trickery and abused done to the poor VIC-II to
> remove borders and such.

For that you stay within the timings of the C64, you just have to write 
to registers at the right time.


> Using the MMU backwards to check for ROM at $e000 and then switching to
> Ultimax mode on access to present the KERNAL is a significant hack I think.

Yes, but for that you have to do things that are outside the normal C64 
timings. You have to make a lot of assumptions on parts speed and do 
multiple things within a clock cycle.

  Gerrit



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