Asmusr Posted September 26, 2014 Share Posted September 26, 2014 Starting a new thread to keep this out of the Sabre Wulf thread. I believe Tursi is right when he concluded that the only way to overrun the VDP is "if you set the address then immediately read the data port, but running with no wait states" See http://atariage.com/forums/topic/164410-vdp-overrun-revisited/page-2?do=findComment&comment=2038835 The weird thing is that Classic99 is giving warnings in the debugger about "reading the VDP too quickly" if you just run Extended Basic. Quote Link to comment Share on other sites More sharing options...
Willsy Posted September 26, 2014 Share Posted September 26, 2014 It does it in TurboForth too. Drives me mad as you can't see anything else in the debugger window! Quote Link to comment Share on other sites More sharing options...
Tursi Posted September 26, 2014 Share Posted September 26, 2014 Can't fix it if nobody tells me That said, you /can/ overrun the VDP in the case it's tracking. But, software pushes the rules. That's not unusual. If you go look at the parts it's complaining about, you'll see setting an address, then reading VDP data on the next instruction. 1 Quote Link to comment Share on other sites More sharing options...
Willsy Posted September 27, 2014 Share Posted September 27, 2014 Right. But in the case of TF all VDP access code is in the 8-bit cartridge ROM, which (I thought) couldn't overrun the VDP! :-) Quote Link to comment Share on other sites More sharing options...
Asmusr Posted September 27, 2014 Author Share Posted September 27, 2014 The XB case is also from 8-bit ROM. Quote Link to comment Share on other sites More sharing options...
Willsy Posted September 27, 2014 Share Posted September 27, 2014 Right. I believe Tursi's statement (see post #1) to be true; his research was very extensive. It's probably just a glich in Classic99. Personally, I'd like a switch to enable/disable VDP overrun detection. Something in Classic99.ini would be fine, no need to mod the GUI for it. Quote Link to comment Share on other sites More sharing options...
Tursi Posted September 27, 2014 Share Posted September 27, 2014 Oh, stop blaming me and just fix your code. 1 Quote Link to comment Share on other sites More sharing options...
Gazoo Posted September 27, 2014 Share Posted September 27, 2014 Oh, stop blaming me and just fix your code. Yeah, that's what NOP's are for! Quote Link to comment Share on other sites More sharing options...
Willsy Posted September 27, 2014 Share Posted September 27, 2014 Nops schmops! 1 Quote Link to comment Share on other sites More sharing options...
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