mos6507's Blog - Magic writes and RF noise

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Delicon is still using RF with his 6-switch and it is particularly bad RF at that. He noticed that Chimera caused a lot of interference. For those with Cuttle Carts, that's not unexpected. But he wasn't happy with it. One thing we noticed is that when he put a resistor pack on the cart lines, it eliminated most of the interference. The problem is that the resistor pack has to also enable the magic write feature. For a while it didn't seem like we could both reduce interference AND enable magic writes. But last night it looked like we found a happy medium with a resistor value that works in both applications. He noticed that RF noise was actually less than you see with a traditional cartridge.

 

We are still concerned about how different models of 2600 will behave with magic writes. So far it has been tested to work with a 6-switch, a 4-switch, and my 1st gen 7800 w/expansion port. My cart has only a 47ohm resistor. I'm assuming my 4-switch and 7800 would work equally well with the higher resistor value Delicon is using on his end. This is something that will require beta testing. We are going to have to find out how Coleco Geminis, Jr's, latter-era 7800s, 5200 adapters, etc... work.

 

The designers of 2600 boards certainly never anticipated this trick. Magic writes are a serendipitous feature which may or may not have a narrow tolerance for signal levels on some systems. Maybe those in-the-know could weigh in on whether we are being too paranoid about this or not.

 

 

 

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