+-^CrossBow^- Posted February 4, 2021 Share Posted February 4, 2021 On 2/2/2021 at 10:17 AM, SpiceWare said: Hardcore. Glad we went the Data Stream route, if we get something wrong we usually still get a screen, just with graphical glitches. The usually because it will fail if the data stream that was wrong was used for flow control, as it contains a list of ROM addresses to jump to. I have mentioned this before, but I use the old Parrot demo to test bus stuffing on 7800s. Clipping C64 gets that demo and the others working each time. So not sure if that helps? Quote Link to comment Share on other sites More sharing options...
+SpiceWare Posted February 4, 2021 Share Posted February 4, 2021 1 hour ago, -^CrossBow^- said: I have mentioned this before I don't recall hearing about clipping C64 before. Did a quick search and see you've mentioned it quite a bit, but doesn't appear to have been in a topic I usually follow. While it doesn't help me, it might help @batari. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted February 4, 2021 Share Posted February 4, 2021 38 minutes ago, SpiceWare said: I don't recall hearing about clipping C64 before. Did a quick search and see you've mentioned it quite a bit, but doesn't appear to have been in a topic I usually follow. While it doesn't help me, it might help @batari. Well, what really bakes the noodle on this. Is that you can start up the parrot demo or any of the bus stuffing demos, you usually get scrambled lines on the screen. While that is happening, you can then switch C64 out of circuit, and it will instantly show you the demo without having to reset the console or any thing. That tells me that the issue is specifically a video output issue and not something on the main logic level of the code? If it were, it would require having to reboot the system after taking C64 out of circuit to get it come up right. You can literally enable/disable C64 while the demo runs to see the effect on and off. Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted February 5, 2021 Share Posted February 5, 2021 19 hours ago, -^CrossBow^- said: While that is happening, you can then switch C64 out of circuit, and it will instantly show you the demo without having to reset the console or any thing. Remind us, please - what is C64 doing? Is it a filtering cap tying something to ground? Neither of my systems has that cap. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted February 5, 2021 Share Posted February 5, 2021 6 minutes ago, DrVenkman said: Remind us, please - what is C64 doing? Is it a filtering cap tying something to ground? Neither of my systems has that cap. It is part of the extra timing circuit that was added in the later revisions of the 7800 and then removed again, in even later revisions. The cap looks like a resistor but is actually a banded ceramic cap and usually green in color. If present you will find it in the dead center between two small 74x logic ICs in the right hand center side of the board. It seems to only affect the timing of the video since the actual game logic isn't affected by removing this. It is the cause of scrambled screens on most of the bus stuffing demos for the 2600, the cause for some of the activision games to not work etc. But again you can literally boot up a game that doesn't work with it enabled, clip the leg in real time and as soon as you do that the game screen comes up without a reset of the system. Put it back in circuit while up and running, and the game screen will go haywire again. But to get back ontopic in regards to TIA... @Andrew Davie, what brand of TIA are you working with here? I just posted something interested in my blog in regards to TIA issues between two different manufactures of TIA in a 7800 I discovered. Quote Link to comment Share on other sites More sharing options...
+Andrew Davie Posted February 5, 2021 Author Share Posted February 5, 2021 17 minutes ago, -^CrossBow^- said: @Andrew Davie, what brand of TIA are you working with here? I just posted something interested in my blog in regards to TIA issues between two different manufactures of TIA in a 7800 I discovered. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted February 5, 2021 Share Posted February 5, 2021 5 minutes ago, Andrew Davie said: Just be curious if you had another PAL TIA on hand to swap it out with, if you still had the same issue? We know that different TIAs are out there and that later ones especially have issues. But you have what looks to be an early '81 produced TIA so I wouldn't think it would be a troublesome TIA. Quote Link to comment Share on other sites More sharing options...
+Andrew Davie Posted February 5, 2021 Author Share Posted February 5, 2021 Just now, -^CrossBow^- said: Just be curious if you had another PAL TIA on hand to swap it out with, if you still had the same issue? We know that different TIAs are out there and that later ones especially have issues. But you have what looks to be an early '81 produced TIA so I wouldn't think it would be a troublesome TIA. A bit difficult at the moment; this is the machine I may have semi-killed with my joystick madness. At the moment it smells a bit like burned stuff and the joystick button is always pressed. I broke something. Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted February 5, 2021 Share Posted February 5, 2021 2 minutes ago, Andrew Davie said: At the moment it smells a bit like burned stuff and the joystick button is always pressed. I broke something. With luck you’ve only fired a filter cap or something. Trigger lines are read by TIA, so you may end up needing to swap that chip anyway. Quote Link to comment Share on other sites More sharing options...
+Andrew Davie Posted February 5, 2021 Author Share Posted February 5, 2021 1 minute ago, DrVenkman said: With luck you’ve only fired a filter cap or something. Trigger lines are read by TIA, so you may end up needing to swap that chip anyway. Fortunately, we appear to have a fixed glitch-free kernel for PlusCart, so I can just retire this machine and be more careful with another. Quote Link to comment Share on other sites More sharing options...
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