I didn't want to drag up my old thread about C64->VIC tape compatibility, and this is kind of a different question anyway (which I may already have asked in the past? Sorry, my mind is like a sieve :S)
My question is this: will a tape recorded on a PAL VIC-20 (using the standard kernal save) load on an NTSC VIC-20? It looks like I may be doing Psytronik's tape duplication for Carling The Spider but I only have a PAL VIC-20 and a PAL C64 here. I have an NTSC version of the game, which Kenz can duplicate on disk no problem, but just not sure whether I'm equipped to duplicate the tape version. Come to think of it, is it even worth providing an NTSC tape, don't all americans hate tapes?
I believe it is supposed to work. However many years ago I had problems converting WAVs of PAL VIC-20 tapes into TAP, despite the software supposedly should support the VIC. It turned out it did support NTSC clock, which is closer to the C64 clock. Possibly a real VIC-20 is slightly more forgiving than a PC software is. I managed to patch the software with a different clock constant and it worked.
Since I own both PAL and NTSC VIC-20's, if I get some spare time I can try and see how well it works. I can even throw in a PAL C64 and a PET in the tests, albeit no NTSC C64 since I only own a NTSC SX-64 that lacks tape support.
carlsson wrote:I believe it is supposed to work. However many years ago I had problems converting WAVs of PAL VIC-20 tapes into TAP, despite the software supposedly should support the VIC. It turned out it did support NTSC clock, which is closer to the C64 clock. Possibly a real VIC-20 is slightly more forgiving than a PC software is. I managed to patch the software with a different clock constant and it worked.
Since I own both PAL and NTSC VIC-20's, if I get some spare time I can try and see how well it works. I can even throw in a PAL C64 and a PET in the tests, albeit no NTSC C64 since I only own a NTSC SX-64 that lacks tape support.
I can vaguely remember one of the common wav/tap/prg conversion tools stating that it supports VIC but then doesn't seem to handle it any differently than C64, maybe this is the same thing you were talking about above.
If you'd be willing to give it a try any time soon that would be most appreciated. I could give you a copy of the NTSC game on D64 which you could record to tape on your PAL VIC-20 and then try and load it on your NTSC VIC-20. The game still hasn't had an NTSC hardware test so maybe you could take a look at the game itself too?
Unfortunately I have no good monitor that can display NTSC in colour, only B&W. The only option for me is to use my PC video capture card.
However I would be able to try your game to see that things are visible at all, no bad timings, sound and so on. Send me an PM, I just got a three day weekend in front of me with nothing particular planned.
As a rule of thumb, tapes that have been recorded by a machine of a certain CPU frequency can be read with a machine of the same, or a higher CPU clock.
I distinctly remember I could even read back VIC-20 tapes (PAL) on a C128, if I had put it into FAST mode first!
0.985248 MHz (C64 and C128 PAL)
1.022727 MHz (C64, C128 and VIC-20 NTSC)
1.108405 MHz (VIC-20 PAL)
1.970496 MHz (C128 PAL FAST mode)
2.045454 MHz (C128 NTSC FAST mode)
So, if you record the tape on a PAL C64 it should be readable on both PAL, and NTSC VIC-20s.
carlsson wrote:By the way, I completely forgot about this. Sorry, but I suppose I can do it some evening.
Thats ok, until I know otherwise I can go by the table posted above. It sounds like it'll be VIC-20 PAL recording for VIC-20 pal (obviously ) and C64 PAL for VIC-20 NTSC. And it'll probably be both versions on the same tape.
Now I have made some practical testing. I've been using Joe's new game as a basis for testing. It consists of a small intro part (5 blocks) and the main game file (14 blocks). I didn't observe any difference in loadability between a short and longer file.
PAL C64 recording (0.98 MHz): Readable on PAL C64, NTSC VIC-20, and PAL VIC-20
NTSC VIC-20 recording (1.02 MHz): Readable on PAL C64, NTSC VIC-20 and PAL VIC-20
PAL VIC-20 recording (1.11 MHz): Readable on NTSC VIC-20 and PAL VIC-20, garbage on PAL C64
This corresponds pretty much to what I knew from before. Apart from the basic rule that you can load a tape on a faster machine than it was recorded on, it seems a slower machine indeed can read a tape recorded at higher frequency if the difference is at most 0.1 MHz.
I think the reason why I failed to read VIC-20 tapes to PC before was that the PC software had much less tolerance than a real Commodore computer has, thus in the PC software you need to exactly specify what kind of data you read or record.
Anyway, it seems you can use a PAL C64 to duplicate tapes, and still get them readable on both kinds of VIC-20's.
) and C64 PAL for VIC-20 NTSC. And it'll probably be both versions on the same tape.