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johncl
Registered: Aug 2007
Posts: 37 |
Turbo Tape, how does it work?
I have always been curious about how turbo tape really worked. I know that the tape drive originally could only read 50 bytes per second which would take a whopping 21 minutes to fill up the whole memory. I was always under the impression that games used compression to speed up tape loading (Just did a test with Giana Sisters which took 4 minutes to load).
Did Turbo Tape fiddle with the speed that data was written and read to the tape? I didnt think that was possible (only thought that was how they sped up disk reading/writing). If anyone got a good resource at how e.g. the well known Turbo Tape works, please post a linky here. |
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johncl
Registered: Aug 2007
Posts: 37 |
Ahh, thanks for clearing that out. I didnt know you had such a low level access to the tape read/write mechanisms that enables you to actually time pulses.
So to further discuss this, what did most commercial games use? For example Novaload which I know a number of distributors used. I guess they couldnt squeeze it as low as Turbo Tape as that would probably have ended up with the game not working on some tape drives (and couldnt handle any kind of error).
You see, I am quite surprised at the fact that close to 100% of the old tapes I have tried still load perfectly after 20-25 years of storage (and I mean all sorts of storage since these are bought from around the world). In fact, only one tape has bugged out on me in which the tape drive was not even able pull the tape after 3 count ticks into the tape start. :) |
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Martin Piper
Registered: Nov 2007
Posts: 722 |
Cyberload/Novaload etc don't handle the potential for the really slow or fast tape drive wobblyness so I suppose it was never much of an issue. Basically, don't bother writing code to calibrate the timings because they're not that much of an issue compared to the cycle timing wobbles you can get when displaying a picture during loading.
Unless you have the screen turned off and want to make a really fast loader. But in my experience the time differences you can get on a real C2N during loading change due to the amount of tape on each spool. Or if the pet dog walks past the C2N. :) |
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Graham
Account closed
Registered: Dec 2002
Posts: 990 |
I believe that much faster turbo tape formats are possible. The main problem with the existing fast tape stuff is, that those routines always use hardcoded thresholds for 0 and 1. This causes problems if you move from one tape drive to the next so the threshold has to be chosen in such a way that the 0 and 1 ranges are quite big. If you manage to measure the tape drive speed first, you might be able to use much smaller pulse lengths -> faster loading + more data on a tape.
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algorithm
Registered: May 2002
Posts: 705 |
There was the SuperTurbo format which was used in the Action Replay Cartridge which i believe was nearly twice as fast as Turbotape. I dont think there was any other loader which would load data this fast commercially but that is understandable as it could have caused more possibility of error |
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Martin Piper
Registered: Nov 2007
Posts: 722 |
Re: Action Replay super turbo. If the assumption is made that the C2N doing the saving is going to be the C2N that will be doing the loading then it's possible to make the bit rate quicker without any fancy timing calibration. :) |
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johncl
Registered: Aug 2007
Posts: 37 |
Hm, did any of these fast loaders/savers do real time compression/decompression of data? E.g. RLE compression? |
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enthusi
Registered: May 2004
Posts: 677 |
There is also supertape format.
3600 baud used in Input64 tape-mag.
It has the option to save/load in high speed mode as well.
7200 baud. Would make it hellish fast too but too unreliable to be called a proper load/save I"d say.
Same goes for that AR-Superturbo. Even the manual says: dont use it when you need your data.
About graham: yeah, the ROM-load sets the thresholds according to sync-signal. TurboTapes SHOULD/could really do that too.
Maybe you dont have to wait all too long to see it done :) |
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johncl
Registered: Aug 2007
Posts: 37 |
Hehe at 7200 baud you could do a tape movie playback that updated a 7x7 charset image at 2 frames per second! Imagine the quality video you could have (and a few errors here and there wouldnt be too annoying). |
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algorithm
Registered: May 2002
Posts: 705 |
Quote: Re: Action Replay super turbo. If the assumption is made that the C2N doing the saving is going to be the C2N that will be doing the loading then it's possible to make the bit rate quicker without any fancy timing calibration. :)
Yes certainly. Infact the data could be saved with more density. Superturbo was just below 1k a second if i remember rightly. |
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enthusi
Registered: May 2004
Posts: 677 |
@johncl the problem with tape loaders is not flipped bits.
That wouldnt hurt and would be rather simple to correct, but MISSING bits. (or extra bits)
Those are pure evil hell to deal with... |
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