On Sat, 22 Aug 1998, Stephen Judd wrote: > In part I was wondering if this is a trial and error kind of thing, or > if a more precise calculation may be applied, e.g. for every x cycles, > add y cycles. My naive MHz calculation says that around 50 drive cycles > is about 51 NTSC cycles (or 49 PAL cycles) -- in other words, that > they stay more or less in sync for a pretty long time. Is it really > a matter of a single cycle in just the right place? I think yes. The best fastloaders transfer 128 or 256 bytes in a row without any explicit synchronization. The trick is to monitor the serial bus and add a branch to the next address, i.e. something like bit serialbus:bmi .+2. Every time the line changes (one cycle) too early, the code will spend an extra cycle. (Remember, a taken branch adds 1 cycle, or 2 cycles if the target is on a different page.) The best fastloader I have seen is in the Action Replay cartridge. I also have a copy of Action Replay 5.2 for NTSC, but I haven't had time to make any comparisons between the NTSC and PAL versions of Action Replay's disk routines. Marko - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail email@example.com.
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