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Were there ever compatibility problems between different versions of the VIC 20?
Posted: Wed Dec 16, 2020 2:33 am
by 16KVIC20
Obviously there was the original two prong VIC 20, and then the Cost Reduced Version; were there any compatibility issues between the two machines? I obviously know about expansion compatibilty issues 3K/8K/16K/32K/35K, that's not what I'm talking about.
I just remember there were some games (don't ask me which ones now!) that my friend with a 2 Prong machine leant me years ago that would not load on my CR model for love nor money.
Re: Were there ever compatibility problems between different versions of the VIC 20?
Posted: Wed Dec 16, 2020 3:33 am
by tokra
I don't think such issues have been observed in the last 40 years. There is of course the incompatibility between PAL and NTSC when using raster-effects, but other than that I know of no issues that would affect compatibility. On the C64 you have slightly different CIAs and of course the C128 that is a little different in C64-mode, but I am not aware of anything like that on the VIC.
Re: Were there ever compatibility problems between different versions of the VIC 20?
Posted: Wed Dec 16, 2020 4:01 am
by srowe
The only significant difference (of a digital nature) between the original version and the CR was the change of RAM from 2114s to 2016s. This shouldn't be detectable by software. All other changes are either on the video or power circuits.
Re: Were there ever compatibility problems between different versions of the VIC 20?
Posted: Wed Dec 16, 2020 5:19 am
by Vic20-Ian
16KVIC20 wrote: ↑Wed Dec 16, 2020 2:33 am
Obviously there was the original two prong VIC 20, and then the Cost Reduced Version; were there any compatibility issues between the two machines? I obviously know about expansion compatibilty issues 3K/8K/16K/32K/35K, that's not what I'm talking about.
I just remember there were some games (don't ask me which ones now!) that my friend with a 2 Prong machine leant me years ago that would not load on my CR model for love nor money.
What was it that you could not load, was it some of his purchased tapes or something he saved?
It is far more likely to be something he saved on his C2N with different tape head alignment to your C2N deck causing load errors.
Re: Were there ever compatibility problems between different versions of the VIC 20?
Posted: Wed Dec 16, 2020 5:21 am
by Vic20-Ian
Vic20-Ian wrote: ↑Wed Dec 16, 2020 5:19 am
16KVIC20 wrote: ↑Wed Dec 16, 2020 2:33 am
Obviously there was the original two prong VIC 20, and then the Cost Reduced Version; were there any compatibility issues between the two machines? I obviously know about expansion compatibilty issues 3K/8K/16K/32K/35K, that's not what I'm talking about.
I just remember there were some games (don't ask me which ones now!) that my friend with a 2 Prong machine leant me years ago that would not load on my CR model for love nor money.
What was it that you could not load, was it some of his purchased tapes or something he saved?
It is far more likely to be something he saved on his C2N with different tape head alignment to your C2N deck causing load errors.
Or
Was it perhaps a tape he copied tape to tape on a stereo rather than a Commodore tape deck?
Re: Were there ever compatibility problems between different versions of the VIC 20?
Posted: Wed Dec 16, 2020 7:17 am
by groepaz
srowe wrote: ↑Wed Dec 16, 2020 4:01 am
The only significant difference (of a digital nature) between the original version and the CR was the change of RAM from 2114s to 2016s. This shouldn't be detectable by software.
Perhaps those result in a different power up (non initialized) RAM content? There are a surprising number of vic20 programs that rely on this.
Re: Were there ever compatibility problems between different versions of the VIC 20?
Posted: Wed Dec 16, 2020 7:54 am
by 16KVIC20
Vic20-Ian wrote: ↑Wed Dec 16, 2020 5:21 am
Vic20-Ian wrote: ↑Wed Dec 16, 2020 5:19 am
16KVIC20 wrote: ↑Wed Dec 16, 2020 2:33 am
Obviously there was the original two prong VIC 20, and then the Cost Reduced Version; were there any compatibility issues between the two machines? I obviously know about expansion compatibilty issues 3K/8K/16K/32K/35K, that's not what I'm talking about.
I just remember there were some games (don't ask me which ones now!) that my friend with a 2 Prong machine leant me years ago that would not load on my CR model for love nor money.
What was it that you could not load, was it some of his purchased tapes or something he saved?
It is far more likely to be something he saved on his C2N with different tape head alignment to your C2N deck causing load errors.
Or
Was it perhaps a tape he copied tape to tape on a stereo rather than a Commodore tape deck?
They were original releases. Two that I do recall, now I come to think of it are Wacky Waiters and Catcha Snatcha. I think also a few Romik titles.
A few years into my VIC 20 adventure, I found a short 3 line program that consisted mostly of POKEs, IIRC that seemed to improve loading, I had to use it to get Audiogenic Golf to work.
Re: Were there ever compatibility problems between different versions of the VIC 20?
Posted: Wed Dec 16, 2020 7:55 am
by 16KVIC20
groepaz wrote: ↑Wed Dec 16, 2020 7:17 am
srowe wrote: ↑Wed Dec 16, 2020 4:01 am
The only significant difference (of a digital nature) between the original version and the CR was the change of RAM from 2114s to 2016s. This shouldn't be detectable by software.
Perhaps those result in a different power up (non initialized) RAM content? There are a surprising number of vic20 programs that rely on this.
Could be onto something there perhaps. I'd be surprised if there were no compatability issues, it's something that Commodore seemed to excel at! It could equally be my C2N unit was a bit off. Mine was the later version, the rounded one, with save LED on the left and a glass screen over the counter, black on white numbers. His was the Pet style version. Maybe earlier games worked better with that style of C2N?
Re: Were there ever compatibility problems between different versions of the VIC 20?
Posted: Thu Dec 17, 2020 2:26 am
by Mike
The description of the issue at hand is pretty vague. You neither name the programs/games affected nor the symptoms.
As some of the previous posters already had pointed out, the change of the RAM chips is the single most important difference between the two main board revisions (2-prong vs. CR). That affects the RAM contents immediately after power on. The KERNAL only clears pages 0, 2 and 3 (i.e. $0000..$00FF and $0200..$03FF) in the reset routine, and the RAM check is non-destructive.
16KVIC20 wrote:I'd be surprised if there were no compatability issues, it's something that Commodore seemed to excel at!
Programs that rely on contents of un-initialised RAM are broken by design. No reason to cast blame on the CBM engineers for this.
Re: Were there ever compatibility problems between different versions of the VIC 20?
Posted: Thu Dec 17, 2020 2:42 am
by 16KVIC20
Mike wrote: ↑Thu Dec 17, 2020 2:26 am
The description of the issue at hand is pretty vague. You neither name the programs/games affected nor the symptoms.
Actually I named two programs. The symptom was simply that they would not load. IIRC one of them did load eventually, but was corrupted. We are actually talking about events that toook place 37 years ago, so pardon me if I don't recall it all verbatim.
16KVIC20 wrote:I'd be surprised if there were no compatability issues, it's something that Commodore seemed to excel at!
Programs that rely on contents of un-initialised RAM are broken by design. No reason to cast blame on the CBM engineers for this.
Oh dear me, I was being lighthearted...
I suppose in many ways the software houses are the people that really make or break a machine, at least for gaming. Any changes that a manufacturer makes to their machines that affects compatibility could therefore be an issue. It's not a question of blame, just the obvious. If it's only a few games, as was probably the case, then no big deal, but I just wondered if it was a thing that others had ever noticed, or was known about.
Re: Were there ever compatibility problems between different versions of the VIC 20?
Posted: Thu Dec 17, 2020 6:44 am
by Noizer
Vic20-Ian wrote: ↑Wed Dec 16, 2020 5:19 am
16KVIC20 wrote: ↑Wed Dec 16, 2020 2:33 am
(...)
(...)
It is far more likely to be something he saved on his C2N with different tape head alignment to your C2N deck causing load errors.
I can confirm. All problems from back then were mainly caused by different badly set azimuth screws by the owner of the Datasettes and compatibles. Sometimes the self-proclaimed well-known expert had made things worse.
Then there were the bad copies of copies of copies etc. made with stereo tape decks. Those were the times when tools for adjusting came out.
I personally just soldered a loudspeaker with a switch on the data output line. Loud enough and pretty efficient to adjust the azimuth screw!
The problems were forever eliminated for me after switching to the 1541 drive.
So i don't miss the tapes at all. If you still use tapes, apart from the retro experience, it is your own fault.
Re: Were there ever compatibility problems between different versions of the VIC 20?
Posted: Thu Dec 17, 2020 7:40 am
by Vic20-Ian
Noizer wrote: ↑Thu Dec 17, 2020 6:44 am
Vic20-Ian wrote: ↑Wed Dec 16, 2020 5:19 am
16KVIC20 wrote: ↑Wed Dec 16, 2020 2:33 am
(...)
(...)
It is far more likely to be something he saved on his C2N with different tape head alignment to your C2N deck causing load errors.
I can confirm. All problems from back then were mainly caused by different badly set azimuth screws by the owner of the Datasettes and compatibles. Sometimes the self-proclaimed well-known expert had made things worse.
Then there were the bad copies of copies of copies etc. made with stereo tape decks. Those were the times when tools for adjusting came out.
I personally just soldered a loudspeaker with a switch on the data output line. Loud enough and pretty efficient to adjust the azimuth screw!
The problems were forever eliminated for me after switching to the 1541 drive.
So i don't miss the tapes at all. If you still use tapes, apart from the retro experience, it is your own fault.
I think this was an exploratory post about compatibility issues between Vic20 variants based on experience 37 years ago not currently but yes the tape issues were often copies or saving on a friend's tape deck not working on yours due to Azimuth.
I never had any big problems on the Vic20 but the C64 was bit more sensitive with Novaloads etc. iirc. That was when the Azimuth alignment kits came out.....A cheap screwdriver and a cardboard arrow
Re: Were there ever compatibility problems between different versions of the VIC 20?
Posted: Thu Dec 17, 2020 9:19 am
by 16KVIC20
I think this was an exploratory post about compatibility issues between Vic20 variants based on experience 37 years ago not currently
Exacly this Vic-20Ian yes
but yes the tape issues were often copies or saving on a friend's tape deck not working on yours due to Azimuth.
Agreed, and this is quite understandable. A proper game though, that is less likely, especially when it loads on one VIC 20, but not another.
I never had any big problems on the Vic20 but the C64 was bit more sensitive with Novaloads etc. iirc. That was when the Azimuth alignment kits came out.....A cheap screwdriver and a cardboard arrow
I never touched the azimuth screw on my C2N, I think I learnt my lesson on another tape deck. Now I do have an azimuth adjustment program for the C64, using that I adjusted my 1530/1531 decks to optimum performance. I don't use them much, but it's nice to have a back up, and to know that they're set up just right.
I suppose one way to settle this is to get a download for Wacky Waiters and Catcha Snatcha and see if they load on my CR VIC 20.
