Recommended Demos

[Gorf]

I was thinking about it and I don't have many programs in the way of demos for my VIC. Does anyone have any recommended demos that I should check out?

[mrr19121970]

Impossiblator 1-3

http://www.pouet.net/prod.php?which=31537

[Gorf]

Ok, thank you! I'll have to check them out.

[orion70]

One of my all-time favs:

Robotic Liberation (unxpanded):
http://www.pouet.net/prod.php?which=10626

Robotic Liberation (16k):
http://www.pelulamu.net/pwp/vic20/rl-16k.prg

All the Others (three pages ): http://www.pouet.net/prodlist.php?type% ... +20&page=1

Have fun

[Mike]

I take it you're from NTSC country. Unfortunately, the majority of recent demos were developed on PAL machines, and will only work on PAL VIC-20s. That also includes the demos you were pointed to in this thread so far, i.e. the Impossiblator series and Robotic Liberation.

Those demos rely on exact timing during screen display - an effect "timed out" for PAL doesn't work out of the box for NTSC and vice versa. Also, the screen dimensions are different, PAL is capable to show a lot more pixels (i.e. is has a wider overscan area); NTSC on the other hand has interlace capability which can be used to increase the vertical resolution. PAL VIC-20s can't do interlace.

Another issue is a probable dependance on the drive. Quite some demos reprogram the drive for (at least slightly) faster data transfers, and these transfer routines also allow to continue the effects, while loading the next part proceeds in the background. SD2IEC drives can't be reprogrammed this way and are confined to either the standard CBM DOS IEC protocol, the JiffyDOS protocol (and those two don't allow for transfers in the background) - some other fastloader protocols from the C64 have been re-implemented in the sd2iec firmware which could be utilized, but thus far no-one had written compatible routines for the VIC-20.

So, it's mainly hit-or-miss for NTSC and SD2IEC regarding current demos.

You could try out Part 16 of tokra's and mine graphics series, which shows colourful hires pictures on an NTSC VIC-20. You find them here:

** New Frontiers in VIC-Hires-Graphics, Part 16

Greetings,

Michael

[Gorf]

Ok, thank you for your response. You would be correct that I am from the NTSC region. I figure I'll try the demos anyway once my SD2IEC comes just to see what happens.

Thank you for the recommendation on the demo, I will certainly have to check it out!

On a side note, I might want to get a PAL VIC to allow me to use more software.

Is there anything that would allow NTSC VICs to display PAL graphics correctly?

[Mike]

Is there anything that would allow NTSC VICs to display PAL graphics correctly?

As soon as a program uses the aforementioned programming techniques, which rely on the exact number of cycles per line and the exact number of cycles per frame, then no. Unless it provides the necessary routines for both TV systems - and the effect allows to be ported between PAL and NTSC, i.e. it can be "expressed" within the hardware limits available on both systems. In practice, this means the lowest common denominator for both. Each one of them can do things the other one cannot. In the latter case, a port cannot be done.

It's also of no use to put a PAL->NTSC converter into the video cable when running a strictly PAL-only program on an NTSC VIC-20: that's an idea a Denial fellow brought up years ago, most probably in the hopes that the program now somehow would produce "PAL output" and that this would be the reason it wouldn't show correctly on NTSC displays. Actually, the video chip still produces NTSC output, and that output is just deranged, because the effects timed out for PAL cannot sensibly synchronise to NTSC timing. Either the output is deranged, or the program crashes rightaway.

...

As an example, you might take a look at the Pokémon picture I did in 2016. The picture exactly uses such raster effects to increase the number of simultaneously visible colours and it actually provides routines for both PAL and NTSC - the files on disk called "PAL ENGINE" and "NTSC ENGINE".

The main program on disk checks in line 1, what TV system your VIC-20 has, and then loads the corresponding engine:

Code: Select all

1 POKE55,0:POKE56,62:CLR:DN=PEEK(186):N$="PAL":IFPEEK(60900)=5THENN$="NTSC"
2 SYS57809(N$+" ENGINE"),DN,1:POKE780,0:SYS65493:@LOAD"POKEMON 20TH",DN:SYS15872
3 GETA$:IFA$=""THEN3
4 SYS64850:SYS65017:@RETURN

Now, if you change the IF clause in line 1 of the main program from "PEEK(60900)=5" into "PEEK(60900)<>5", you'll make the program load the wrong engine for your TV system. When run once again, the program won't crash - but instead of steady colours you'll just get flickering stripes.

[Gorf]

Ok, thank you for that in-depth explanation. I am definitely considering buying a PAL VIC-20 to allow for me to use more software.

[orion70]

I have tried at least Robotic Liberation with the SD2IEC device, and it works well!

[Mike]

I have tried at least Robotic Liberation with the SD2IEC device, and it works well!

The single load +16K version for sure. You just load that single file, and it doesn't matter whether it has been loaded from a 1541, SD2IEC or whatever else. Once the demo runs, it doesn't anymore access the disk drive and so isn't affected by the drive type.

However, the original "track-mo" version for unexpanded VIC-20 *does* reprogram the 1541 drive and installs alternate transfer routines, and thus will *not* work with a SD2IEC device!

SD2IEC doesn't mean you're necessarily confined to single load programs. Multi load programs are fine as long as they conform to the standard IEC bus protocol or JiffyDOS (with SJLOAD or a JiffyDOS KERNAL in the VIC-20). "going lowres" by TRSI is an example multi load demo that runs fine from SD2IEC. That being said, "going lowres" is another case for a PAL only demo (on an NTSC VIC-20 it crashes right at the start), so that's again where it ends for Gorf's current means.