Re: NTSC VIC-II timing

Date: Wed, 21 Jun 2017 19:12:27 +0200
Message-Id: <>
> On 2017-06-21, at 18:43, Gerrit Heitsch <> wrote:
> Before you do that, check if there are other software detectable differences between the 6567R56A (and older) and the 6567R7 (and newer). Those might be easier to detect.

As just noticed - there is a difference in the number of scan lines, which might in fact be easier to abuse.

> I suggest this since it's possible by software if you have a 6569R1 or a later VIC and if later, if it's a 6569 or a 8565.
> Here's what Segher wrote about it:
> Excellent fun!  It sees if the light pen interrupt can be triggered
> between raster lines x'136 and 2; if so, it's a 6569R1, if not, not.

That's very interesting too! How does one trigger LP IRQ from within software alone? Is it a kind of raster position / CIA port combination?

> The 8565 vs. 6569 test seems to be if sprite-background collision
> is triggered for a sprite with ECM colour 2 (bits 10) (on 8565 it
> is, on 6569 not).

Yes, that one I've seen.

SD! -

       Message was sent through the cbm-hackers mailing list
Received on 2017-06-21 18:00:02

Archive generated by hypermail 2.2.0.