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Didi
Registered: Nov 2011
Posts: 487 |
Advice for fastest 1541 compatible fastloader
I need advice for a very fast non-IRQ fastloader for 1541 compatible drives which is freely available. I've been away for some years, maybe there has been some new developments the past 10 years. |
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Zaz
Account closed
Registered: Mar 2004
Posts: 33 |
So did anyone ever do a (non-GCR) loader that can read a track in one revolution on a stock c64+1541? It should be possible... |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
krill is working on that =) |
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Graham
Account closed
Registered: Dec 2002
Posts: 990 |
Quoting ZazSo did anyone ever do a (non-GCR) loader that can read a track in one revolution on a stock c64+1541? It should be possible...
Only if that format stores less than 2k on that track, because otherwise you cannot buffer it in 1541 RAM :) |
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j0x
Registered: Mar 2004
Posts: 215 |
Assuming Didi wants to use this loader for cracks, the requirement of a track buffer in C64 RAM may be prohibitive. The AR gets around the problem by placing this buffer in AR RAM, but that's cheating :) You can assume ideal sector interleave or you can be clever and load directly to C64 RAM in the order in which the sectors are placed on the disk, but you'll need a full revolution to ensure not writing past the end of file in memory (some sectors in a track may not belong to the current file, and you can't know that unless you've followed the (t,s)-chain).
Edit: Removed question |
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Zaz
Account closed
Registered: Mar 2004
Posts: 33 |
Quote: Quoting ZazSo did anyone ever do a (non-GCR) loader that can read a track in one revolution on a stock c64+1541? It should be possible...
Only if that format stores less than 2k on that track, because otherwise you cannot buffer it in 1541 RAM :)
Of course it would have to stream to C64 while reading.
I actually designed the critical parts of such a loader but didn't complete it because I couldn't think of anything to use it for :) |
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Krill
Registered: Apr 2002
Posts: 2980 |
For plain GCR, Mafiosino's loader should be fastest (around 20x), but it requires a lot of memory to buffer a raw track.
Fastloaders without track buffers (like the loaders written to disk by AR and other cartridges) are around 12x-15x.
If custom encoding with less than 256 bytes per block is an option, Heureka-Sprint is the fastest i know (around 25x, $e0 bytes per block), and it works with plain d64 and standard GCR disk copiers.
As groepaz said, i am currently working on a 50x fastloader (reading, transferring and checksumming a track in one revolution) with a custom encoding that yields $c0 bytes per block, also with d64/standard GCR compatibility. |
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Krill
Registered: Apr 2002
Posts: 2980 |
Quote: Of course it would have to stream to C64 while reading.
I actually designed the critical parts of such a loader but didn't complete it because I couldn't think of anything to use it for :)
Do you still have those bits? I'd like to have a look at that and compare with my ideas for a one-revolution serial fastloader. :) |
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Zaz
Account closed
Registered: Mar 2004
Posts: 33 |
Sounds like you're aiming higher than me with the compatibility and all, but PM me your e-mail and I'll give you an outline. If there's anything new or useful in my design, I'll share whatever I have.
So far it's my own design notes and a spreadsheet of code/cycle timings...
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ChristopherJam
Registered: Aug 2004
Posts: 1409 |
I did create a format that had only one sync per track back in the day; I can't remember whether it took one or two passes to read it, but the only way I managed to write was using a drive that a friend had added a parallel port to (soldered a cable from an IO port on a drive chip to a c64 user port connector).
At the time I was thinking it would be a great way to copy protect a game I was working on. Not so good for demo distribution, mind. |
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Krill
Registered: Apr 2002
Posts: 2980 |
That sounds very much like what the V-MAX! guys did, see http://markus.brenner.de/mnib/vmaxtech.txt. (And as stated there, the later Vorpal doesn't need any hardware syncs at all on a track.)
The hardware sync is not necessarily a sector-starting sync, as they proved, so yeah, your format might have been readable in more than 1 revolution with a vanilla 1541.
What was your aim when coming up with this idea? :) |
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