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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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algorithm
Registered: May 2002
Posts: 705 |
For fast loading speed, simply pack the data as efficiently as possible before saving. I remember most of the games available in the stone ages (ie vendetta) that would load nearly the full 60k of data or so when the load time could have easily halved if the data was packed beforehand |
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iAN CooG
Registered: May 2002
Posts: 3197 |
Quote: For fast loading speed, simply pack the data as efficiently as possible before saving. I remember most of the games available in the stone ages (ie vendetta) that would load nearly the full 60k of data or so when the load time could have easily halved if the data was packed beforehand
mainly because there were nearly no packers at that time, at least before 1985 =) |
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Mace
Registered: May 2002
Posts: 1799 |
Vendetta (c) 1990 |
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algorithm
Registered: May 2002
Posts: 705 |
Quote: Vendetta (c) 1990
And a tonne more of others. If data took long to load, would have also been a good idea to play music, show a picture while next part was loading or even let the user interact in some way (eg subgame - shinobi) etc. Would not make a difference in the complexity of tape mastering as the tape loading would be under priority with everything else running in the background.
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johncl
Registered: Aug 2007
Posts: 37 |
Well, there are some Mastertronic tape titles that does have a minigame in front of it. Invade-A-Load was one of them and I remember its on the Rogue game at least. What I find interesting is that many games had fullscreen bitmap pictures that you could see while it was drawing on the screen, basically adding another 20-30 second to the loading time. :)
Of course it was cool back then as you got tired of staring at a blank screen. When loaders came with Galway music pumping out the mono speakers we never wanted to go back. :) |
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algorithm
Registered: May 2002
Posts: 705 |
Ahh yes, the memories of the rambo music with the picture appearing gradually as the tape was loading the data.. ahhhh |
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algorithm
Registered: May 2002
Posts: 705 |
Quote: Well, there are some Mastertronic tape titles that does have a minigame in front of it. Invade-A-Load was one of them and I remember its on the Rogue game at least. What I find interesting is that many games had fullscreen bitmap pictures that you could see while it was drawing on the screen, basically adding another 20-30 second to the loading time. :)
Of course it was cool back then as you got tired of staring at a blank screen. When loaders came with Galway music pumping out the mono speakers we never wanted to go back. :)
Just surprising that more was not done with it. After all. the IRQ is responsible for the loading and outside of this, it would have been possible for anything to run without distracting the loading at all unless you wanted solid rasters which would mean more complex tape mastering |
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AlexC
Registered: Jan 2008
Posts: 299 |
Quote: Just surprising that more was not done with it. After all. the IRQ is responsible for the loading and outside of this, it would have been possible for anything to run without distracting the loading at all unless you wanted solid rasters which would mean more complex tape mastering
The reason is simple - 1541 came ;) But actually Datassette is one of interesting devices because it's capabilities to store huge amount of data (comparing to 1541) and technical details has been almost forgotten even if it looks simple. There are very few technical documents regarding this device unfortunately. I've learned a lot about it studying Cyberload. |
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algorithm
Registered: May 2002
Posts: 705 |
Tape mastering (eg saving/loading) is very simple. just precise timing and writing values to a location at precise intervals ( i think its memory location 01?) then the loader can be interrupt driven (provided it runs at full priority) to pick up the bits of data saved to tape. The secret is how to place the 0's and 1's. as well as delay timing. As long as the interrupt routine reads all the data, then exits (to allow main loop to execute whatever) and gets back to the interrupt before the next bit appears on tape etc. Anything can occur in the main loop
Although sprites and the screen on can cause problems if the data is more densely packed |
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Martin Piper
Registered: Nov 2007
Posts: 722 |
Multiplexor while tape loading... Hmm...
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