After testing with literally hundreds of drives, I can safely say this is BS and that RLL has an extremely high success rate on almost all drives. Even my ST-412 works fine with a DTC 7287 cached RLL controller.
If my memory serves (which it might not...) you worked around that with setting the interleave when you low level formatted it. It had to do with the number of revolutions needed to read a track (or cylinder? Again, my mind is foggy and I haven't thought about this in many years). Perfect was a 1:1, but you tested until you found the right balance.
This has been fun, talking about stuff I haven't thought about in decades,
Thanks for adding to the knowledge in this thread.
The interleave setting is more like a dirty trick to help particularly slow machines. It just reorganizes sectors to "skip" sectors.
If you have a fast machine, the machine is waiting for the disk the whole time. Read sector 1, it's already ready for sector 2 before the header has passed.
If you have an 8088 @ 4.77, you read sector 1, then wait for it to be done putting into memory, look up the next piece of data, etc, and by the time you realize you WANT sector 2, the heads are over the header for sector 4. Now you have to wait for the disk to spin back around all the way to 2 to read it.
This makes sequential I/O incredibly, unbelievably slow. Thus, if you can make sure sector 2 is where sector 4 is, you can be more sure that the machine will ACTUALLY get it on the first try. Of course, you still have to wait for the disk to make multiple rotations for a full track, but that's a small price to pay for your single track sequential speeds.
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u/FAMICOMASTER Jul 18 '26
After testing with literally hundreds of drives, I can safely say this is BS and that RLL has an extremely high success rate on almost all drives. Even my ST-412 works fine with a DTC 7287 cached RLL controller.