Re: VIC-20 "Pause" button

From: Peter Rittwage <>
Date: Fri, 12 Jul 2013 13:27:43 -0400
Message-ID: <>
There is also a C64 "slowdown" cart which attached the IRQ line to a timer
and potentiometer. It would inject IRQ's to slow down, or pause, the
running program.

It was a simple cart circuit, and it had really odd effects on different

On Fri, Jul 12, 2013 at 1:25 PM, Jim Brain <> wrote:

> I'm sure this is old news to most folks, but I was surprised.
> Leif Bloomquist gave me an old VIC-20 Expansion Unit (6 slot) that
> contains a number of switches and knobs (it's really a cool unit, you can
> select which banks the 2 RAM slots use via knobs, the normal ON/OFF per
> slot, and some DIP switches for configs and a RESET button.).  One
> intriguing item on the PCB was a "PAUSE" switch. Dubious, I set the unit
> up, popped in a GORF, and started the game. Just as the name suggests,
> enabling the "PAUSE" button does indeed pause the game.
> I checked, and the switch just grounds IRQ.  I suppose it makes sense, as
> the CPU would continuously go to the IRQ routine, never moving forward in
> the regular code, but it did surprise me.
> I didn't exhaustively test, but I worked on non cart apps as well.
> thought it odd that I've never seen a simple cartridge with a button
> marketed for the VIC-20 as a "pause your game" aid.  I would have thought
> such a product would have been marketed.
> JIm
> --
> Jim Brain
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Received on 2013-07-12 18:01:22

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