Re: [stella] A new way to bankswitch

Subject: Re: [stella] A new way to bankswitch
From: "Fred Quimby" <c9r@xxxxxxxxxxx>
Date: Wed, 9 Mar 2005 17:36:11 -0500
I thought about that.  It does depend on how fast the hardware operates.  
There is only one cycle between $FFF8 and $FFF9 accesses.  Standard logic 
chips should be more than fast enough for this, it's just that the hardware 
I've seen uses a 0.1 uF capacitor to filter out glitches, and this cap may 
slow down the switching enough to cause this to not work.

Although there are other ways to avoid glitches without a cap and make this 
work 100% of the time, this requires slightly more complex hardware.  The 
litmus test is the standard type with the cap.

The test I'd like to see is if it works on the 8k/16k/32k boards made by 
Pixels Past and available through AA, since if I ever create a game using 
this technique, I'd probably use their boards and these do use caps.  I do 
not have any of these boards so I have no way to test this.  If anyone has a 
board, an eprom burner and few spare moments, I'd appreciate it if they'd 
try it out with the A-team bin that was modified to use this technique, 
which is attached.

>Fred Quimby wrote:
> > So far this has been tested and works in Stella and Z26, and in real
> > hardware on a Kroko cart.  More testing is needed to ensure it will work
> > with various types of bankswitching hardware.
>Very interesting idea.
>But I am not 100% sure it works on real hardware. The problem might
>occur when accessing the RTS at $FFF8. This should switch to bank 1
>(trigger at $FFF9), but also triggers bank 0 immediately before. AFAIK
>this might cause timing problems. At least it did with my first
>Battlezone TC hack, where I used some similar trick. It worked on CC
>and emulators, but not on real hardware.
>Have fun!
>Thomas Jentzsch         | *** Every bit is sacred ! ***
>tjentzsch at web dot de |
>Archives (includes files) at
>Unsub & more at

Archives (includes files) at
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