Denial

Do you remember when I said (and proved with a scope capture) that the regular ripples in the luma signal of the 6560 begins 2 characters BEFORE the text/graphic area and ends 2 characters before the right border ? Haha, sometimes it takes a while for the penny to drop. To be explicit, would you ag...

Actually, I've been attempting to make sense of that document and it appears to be contradictory. It states: First the VIC reads the screen memory and the color memory. This happens after CPU cycle (XPOS + 2*X) + 3 of each rasterline that covers the char. After the following cycle (XPOS + 2*X) + 4 t...

@Tom If that is so then I think what you should do is a plug-in to XVIC rather than create an all-new emulator. I think that what I want from an emulator and what XVic supplies are somewhat divergent. I don't think negatively is warranted because it's an excellent piece of software and the work of ...

btw, VICE also uses this "run until something interesting happens" approach for the CIA and VIA cores. and its exactly what makes this code so terrible and almost unmaintainable :( I used it for a cycle-perfect emulation of a non-Commodore 6502 machine back in the early-'00s; it was defin...

@Tom it feels to me you're more creating a sort of CRT monitor emulator than a VIC-20 emulator. At that point, when you start considering phosphor persistence & al, I guess you should choose whether you're emulating a Commodore 1702, A Sony trinitron TV studio monitor or a junk Magnavox TV set ...

The good news for everybody except me is that I lost my originally typed answer; I appreciate I have some problems with politeness at the best of times but please forgive me if this retelling is unusually brusque. The difference in approaches is between: "Hey, VIAs and VIC, what's the earliest ...

When you can tell me what this code snippet is supposed to do, we can talk further. :mrgreen: I can only assume you haven't read my suggestion and are replying dogmatically. Are you capable of explaining in what scenario a VIA can't tell a priori you how many cycles until its interrupt status will ...

For your other assumptions about the 'necessary' accuracy: you'll have to run CPU, VIC and both VIAs (especially their timers) in single-cycle lock-step. Again, I'm not persuaded by this. I think you'd be fine with: while (haven't yet run for long enough to complete frame) { let timeUntilVIA1Fires ...

btw, i'd be happy to assist in supporting your emulator in the automatic testsuite that i am working on at the moment (mostly for VICE)... (its fairly easy, only needs a couple simple features in the emu) - let me know if you are interested :) Yes please! I love test suites. Now that the machine is...

Underlying reasoning? I'm writing an emulator because writing emulators is fun. I want to be explicit about this: I have no delusions. There is no objective need for a new emulator. Probably almost nobody will ever use my emulator. VICE is a very good emulator. People should use VICE. However, mine ...

Attached, since I seem to be talking about it a lot without offering any substance, is the mess I currently have. To reiterate: the 6502 should be perfect; the 6560 has a bunch of issues; the 6522 has about a million issues; there is no joystick interface; it's NTSC only; it also emulates the base m...

I'm largely talking to myself now and have no idea of the etiquette here of replying to yourself but I've just found Simon Owen's VIC-20 Emulator for SAM Coupe and Spectrum , which implements a Vic-20 emulator in z80 assembly language for the ZX Spectrum (where it runs at about 1/10th Vic speed) and...

Me and v1and3 noticed an asymmetric waveform clipping starting to occur when the volume is above 8. I found an earlier post on that; it sounded like, depending on your Vic, you'll probably get clipping at the top that clamps to somewhere between the equivalent of all four channels outputting a 1 at...

Did you get any sort of digital read-out other than the graphic? What numbers exactly would you have liked to see? I guess it would now be more appropriate to follow up on that elsewhere... (small aside: I added audio to the emulator last night; based on the latest documentation that it's produced ...

Carrying over from the previous thread, from eyeballing the previous graph in which the VIC's approximation of a sine curve for the colour subcarrier was measured, I got the individual vertical bars as being placed and sized as: Centres: 63, 63, 60.5, 58.5, 57.5, 57, 56.5, 56, 54.5, 53, 51, 48.5, 44...