Virtualc64: Let the user choose the VICII model in the hardware preferences panel

[Alessandro1970]

The introduction of this game has a strange graphic defect in the image of the word "FACES" and I also see a defect in the background mountains on the edge of the screen, if I change the VICII with the American version there is no improvement even worse.

Catalypse (1992)(Genias)[cr Faces][t +4 Faces].d64.zip

[Ottavius]

Ok, I tried this game on Vice and the image of introduction on the bottom is clear while on the VirtualC64 the image is incomplete and there is a strange flicker also on the sides.

[puleyo]

This intro is buggy for me too, than the game is ok.
The image on the screen is broken, some black linees then the brown mountains are missing on the two sides. Why ?

[Alessandro1970]

I tried to download another version but I think the problem is due to a problem in the VICII emulation.
Attention that in the VICE (x64.exe 3.2) it shows the same problems: (It doesn't show graph in the borders too, the mountains are missing).

Instead in the VICE x64sc.exe (ver 3.2) it works perfectly:

[Ottavius]

Vice x64SC.exe has a cycle-based and pixel-accurate VIC-II emulation, but I don't' know the meaning referring the VirtualC64 emulation (differences).

[dirkwhoffmann]

VirtualC64 should behave similar to x64sc (cycle based), so it's a bug. It's most likely due to the timing when certain values show up in certain VIC registers. It would be interesting to know how x64sc behaves when a different VIC model is selected (in contrast to VirtualC64, VICE is able to emulate the hardware difference between different VICII chip models).

[Alessandro1970]

I noticed in VICE (sc version) that:
VICII model: 6572 (PAL-N) = same error of the VirtualC64
VICII model: 6569 (PAL) = ok it works
VICII model: 8656 (PAL) = ok it works

[Example - VICII model: 6572 (PAL-N)] The same problem, mountains are missing...

[Ottavius]

Alessandro You are right, I tried VICE. The intro works with VICII 8656 (PAL) [Custom and Discrete].
I think that VICII 8656 (PAL) is better the the others.

[Alessandro1970]

I do not known if there are differences between 6569 and 8656, I think none.
The 6572 was a sud-american version and it could be the same of the other, there will be some bug in the Vice for that version too.
But I think that MOS 6569 is emulated better, in this demo on VICE there are no bug than other version...If you'll use the 8656 instead the 6595 maybe you'll see, frequently, a nasty vertical lightblue line and something wrong else.

[Royal Arte (final) Booze Design) (side 1).zip

[dirkwhoffmann]

There are indeed subtle differences in respect to timing behavior, i.e., the number of cycles between writing a certain VICII register and the time the new value takes effect. Such differences also exist between the old CIAs and the new ones used in later models. In one CIA model, an interrupt takes effect one cycle later than in the other. Although the VICII hardware differences are very small, they often cause trouble in demos because these programs push the chip capabilities to the extreme.

Good thing is, we have a good test case now for distinguishing both VICII models. In later versions, I'll try to offer multiple VICII chips in the hardware setup. So far, I ignored the hardware differences completely, so I can not even tell which chip model is emulated right now. I suppose, VirtualC64 currently emulates a mixture of both models.

[Alessandro1970]

I have tried these demos on the PC with HOXS64 and I must say that the VICII that is used by HOXS64 is the most 'compatible: all the demos work very well.
The VICII of the HOXS64 could be loaned by the VirtualC64 ?

_As soon as possible I try the geos with georam and 2 disk drives_
This link for Royal Demo works: https://csdb.dk/release/?id=11619

[Ottavius]

Is it this one ?
https://github.com/mamedev/mame/blob/master/src/devices/video/mos6566.cpp
Or into this?
FrodoV4_1b.Src.tar.gz

[Alessandro1970]

No, I do not know.
I just wanted to say that for the tests I've done, the VICII of the HOXS64 seems to me more precise than the one in the VICE .... But this is only my opinion ...

[Alessandro1970]

Hi, now VirtualC64 ver 2.3 beta2 works well for me with this intro:

[dirkwhoffmann]

Strange enough. I did some speed optimization in the VIC code, so there was a real possibility that something is broken now. Interesting to see that it's the other way round this time.

[Alessandro1970]

Great review this 2.3 beta 2:
The Royal Arts demo (look up) works like in the VICE now, the others demo I've tried today (many) all work at the best!!!

[Alessandro1970]

This "custom" VIC II emulation has the best compatibility performance.
At this point I don't know if there is a really need to implement more VICII versions...
Thanks

[dirkwhoffmann]

I let the enhance request open, but set it's priority to "Low"

[puleyo]

Also in my opinion this last emulation of the VIC II (2.4 version) is very good, no problems.
Thank you

[dirkwhoffmann]

393 is a follow up