How to figure out the contents of a mystery tape

[falter]

I have my digital group z80 up and running and have been trying to go through various tapes and see what are on them. One I am having no luck with is a tape marked "Quest III". Pretty sure it's a digital group tape as I think it came in a bundle Marty G sent me a long time ago. Im guessing its a game of some sort. But I don't know if it's a BASIC game and if so, what version (Tiny, maxi, etc) it is, or something else.. or if it even is a digital group tape. Is there any scientific way of figuring that out?

 

[krebizfan]

Finding out if it was a likely DG tape would be to play into a computer app that recognizes the frequencies that were recorded. Something like Audicity should work. DG IIUC had two different tape encoding formats but the frequencies are known. With this information, determining that the tape was for a DG system will be possible. Other steps like locating a leader could help narrow the type of tape.

 

[daver2]

There are converters from an audio file to a text file. The sources are available, but will possibly require some tweaking for the DG format (if that is what you want to do of course).

Dave

 

[falter]

Man I'm glad I finally bought a video/audio capture device. Makes life a lot easier.

I used a Startech vid/aud capture device and played the tape into it. I'm not sure if I had my settings right - even at a volume setting of 2 on the tape recorder, it was peaking at -1db. Looking at the waveform and listening to it, it appears there are several leaders and separate segments. So it may be multiple programs. Here is the wav file.

I suppose one other thing to account for is dg had several different CPU boards, so maybe what's on this tape isn't for the Z80...

Also, does anyone know of any repositories beyond Bryan Blackburn's digital group site of dg software online? I want to build as complete a library of dg software as I can.. these tapes are getting old and some have faded to the point of unusability.

 

[bzotto]

Also, does anyone know of any repositories beyond Bryan Blackburn's digital group site of dg software online? I want to build as complete a library of dg software as I can.. these tapes are getting old and some have faded to the point of unusability.

Herb Johnson looks to have on hand a bunch of audio rips of DG cassettes (scroll to Docs, Cassettes section).

Your wav file seems like a pretty clean rip, I applied the (always useful!) Normalize filter in Audacity to remove the "DC offset", and did the spectrum analysis which shows peaks in the range that suggests it is the so-called "Suding" format (2125 and 2975 Hz). Here's Suding's article describing this format. Looks like you probably have three distinct files in there, but I can't help much beyond that into DG semantics unfortunately.

 

[falter]

Many thanks! Yeah there doesn't seem to be much in the way of software available for download. Also I think one of bytecollector's tiny basic tapes may be labelled wrong, the contents seem to match another tape I have. I've been on a mission to try every game in the Tiny BASIC set from dg.. some of them are pretty.. er.. basic.. lol. There's one kinda dark one that isn't mentioned in their catalog.. russian roulette, basically keep hitting a key until you blow your brains out.. hahah. Doesn't seem to be a way to win that one.

I've tried loading the 'quest' tape into Tiny BASIC, so doesn't seem to be that. Tried 'booting' from it, nope. Guess I can try other BASICs. Could be anything though I suppose, even data files. Just want to make sure I'm not mixing tapes from different systems. I'd assume if it were software designed for 8080 use, it'd work somewhat/okay with a Z80? I know the Z80 breaks compatibility in a couple places.

Ultimately I'd really like to build a nice 'tech time traveller' website with this stuff posted.

 

[Svenska]

The Z80 is basically compatible with 8080 code. If 8080 code breaks on a Z80, then it relies on undefined behaviour and probably won't work on an 8085, either.

 

[daver2]

Not quite true.

There is a minor flag incompatible between the 8080 and the Z80. The parity flag comes to mind, but that may be the result of a confused mind!

The original Altair 8080 BASIC would not run on the Z80 without a patch.

Dave

 

[falter]

Here's a partial capture of a tape that came with my original dg z80 system, entitled "operation toe hold". It seems to be data on there, but the tone sounds different than digital group.

Operation Toe Hold

I suppose it's possible whoever had this system may have had a later system, maybe S100, and the tapes were from that but got mixed in with the dg stuff.

Or maybe this is encoded for phideck? Not sure what kind of recording scheme those use.

 

[krebizfan]

Hughies Hot Tips at https://bytecollector.com/dg_docs.htm explains the PhiDeck encoding method. The start of a block should be at 4000 Hz which is distinctive enough to quickly determine if the file was recorded by the DG PhiDeck.

The file does look like it would have the 3 frequencies needed for the GCR recording technique but its late enough that mistakes are likely on my part.