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Ah now I remember something. Actually I first noticed this in the emulation code in MAME, and then too I was thinking "what the heck is going on there?". It turns out that this NAND gate and /DIAG is a new thing, added in the models which do have the piezo speaker thingie. If you look at the...

I don't think that's right. (Sorry for jumping in in an old thread, but since I have been quoted via the PETdoc document upthread I feel somewhat involved :) The Diagnostic Sense line (pin 5 on the user port) connects to PIA 1's PA7 pin, one of the 2 8-bit ports. Sound is created with CB2 from...

I'm pretty sure, I copied it from a cursor disk image myself... Nice! Yes, it's from before my current improvements. Once I'm happy with them, I should replace it.

That's just how the code that I'm playing with works... and I'd like to show you a screen shot of the result. The desired image in the middle is pretty stable. The garbage jumps left and right rather quickly. That's not so strange, since even though the IRQ happens at a fixed time, the CPU...

My current plan is like so: - at the start of each scan line (which is the same as at the end of the previous line), pre-fetch all 40 screen memory values - when the cpu stores to screen memory, after storing it in memory, also determine if it is in the range of the cached values. And if the...

ah yes of course, there is some delay between fetching the data from the screen memory and seeing it on the screen... that would affect how to emulate this, if it were cycle-exact, which it isn't. I've been pondering "when exactly" the emulation renders the scan line, relative to the position...

It is late here too, but in first instance I'm interested in the pre-CRTC timings. I'm not sure if there are any similar demo programs for CRTC-PETs. The emulation code in VICE uses a different criterion for the vertical blank anyway (vsync starts in the "text line" indicated in register 7...

So what you're saying is that the IRQ is triggered 2 cycles after the bottom scan line of the last character on the screen has been fetched. I suppose that means that it happens in the 2nd "phantom character in the border". I think that is actually before the current emulation code runs, and so...

Hi all! I am new to this forum but not new to the PET (it was the first computer I ever used). I am currently the person in the VICE emulator team who does most of the PET stuff. And as a result of this discussion I now have a question :-) There is the HI-RES demo from Cursor (we also have it...