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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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enthusi
Registered: May 2004
Posts: 677 |
check this for precise timing on IRQ tape load :)
A Load of TAP
...what a nice thread... :) |
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johncl
Registered: Aug 2007
Posts: 37 |
Yeah, thats a pretty nice demo showing tape-streaming. I am quite sure there are lots of cool things one could do with it. Still, a scroller is pretty cpu consuming so obviously perfect timing is necessary to be able to use this for example a game or something. Although I guess one would be bored at rewinding the tape for every time one wanted to play again. :)
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Mace
Registered: May 2002
Posts: 1799 |
Quote:Although I guess one would be bored at rewinding the tape for every time one wanted to play again. :) That is easily fixed by putting the demo on both sides of the tape ;) |
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algorithm
Registered: May 2002
Posts: 705 |
Quote: Quote:Although I guess one would be bored at rewinding the tape for every time one wanted to play again. :) That is easily fixed by putting the demo on both sides of the tape ;)
Or make the demo two sided :-} |
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johncl
Registered: Aug 2007
Posts: 37 |
What I find strange is that they didnt see the potential of the tape drive better. For example, from what I have understood, these tape drives only recorded one track, while most heads actually supported stereo tracks. Why didnt they record on both tracks which could bring the saving/loading down to half. And while they were at it they could have recorded both "sides" at the same time which would make it 4 times faster. Although that would require the user to always put the tape on the correct side since they would still use the standard tape drive.
I guess it was because they could reuse existing hardware to make it as cheap as possible and once it was established there was no way they could change it. Sad really, imagine tape games loading 4 times faster. |
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algorithm
Registered: May 2002
Posts: 705 |
Quote: What I find strange is that they didnt see the potential of the tape drive better. For example, from what I have understood, these tape drives only recorded one track, while most heads actually supported stereo tracks. Why didnt they record on both tracks which could bring the saving/loading down to half. And while they were at it they could have recorded both "sides" at the same time which would make it 4 times faster. Although that would require the user to always put the tape on the correct side since they would still use the standard tape drive.
I guess it was because they could reuse existing hardware to make it as cheap as possible and once it was established there was no way they could change it. Sad really, imagine tape games loading 4 times faster.
Thats almost the same question as asking why VIC II did not have 16 sprites rather than 8. I suppose a mono signal is more reliable and 'lasts' longer. Besides if the tape drive had the facility along with the rest of the circuitry for the C64 to be able to read two signals, not many people would have purchased the 1541 (Although Random Access is always great)
The only advantage in the tape drive was its storage capacity in comparison to the disk as well as the cheap price. |
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johncl
Registered: Aug 2007
Posts: 37 |
Well, I wouldnt say thats a fair comparison. The VIC chip took quite a bit of research and work to be created. Stereo tape drives had been around for a long time, even 8 tracks had been around so the technology for storing data on the whole tape was already there. And the C64 was only recording pulses, not an accurate analogue stream. Its really a technology that was under-estimated or dumbed down for other reasons.
But your marketing point holds valid, the faster the tape drive, the less motivation to buy the 1541. :) |
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algorithm
Registered: May 2002
Posts: 705 |
I dont think any tape device connected to a computer at that time would be able to save/load two channel streams at once. The signal would have been less reliable without a doubt in comparison to the mono signal.
The Kernal should have had a fastload/save facility. Saving full memory contents in less than 5 minutes and loading would have still been very reliable rather than the ridiculous twice saving of data.
It was too late at the time I suppose. The Kernal was already created just the same as the C2N was created and the tape connector did not have the facility to receive/transmit two signals hence would have to have been userport/cartridge based (perhaps also joyport?)
If you remember later on in the years there was a Rainbow Arts CD with special interface which would load data at a decent speed
Regarding the speed in comparison to 1541 The Turbotape (Particularly Superturbo) was actually faster than 1541 (Without a disk fastload obviously) |
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algorithm
Registered: May 2002
Posts: 705 |
Unfinished Demo 1
The above is a c64 demo created around 14 years ago or so by me. (Please excuse the lame coding and scrolltext) Had no motivation to finish it at the time (What do you expect when coding the entire thing using AR monitor and Tape!)
It was originally part of a multitape demo which contains an IRQ loader. Press space after the demo which starts off the tape loader. Scrolltext, Fading logos and music, although has potential of full demo parts running while data is being pulled off from tape at around the same speed as turbotape. Although solid rasters are not possible using this method |
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Zer0-X
Account closed
Registered: Aug 2008
Posts: 78 |
En example for a bedtime read:
http://oms.wmhost.com/TAP/loaders/SLC_Flimbo's_Quest.txt
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